KRILL - Kerbal Rebindable Inputs & Limitless groups

A Kerbal Space Program mod that extends the stock action-group system past its 10-group limit transparently. Groups 11 and up work exactly like groups 1-10 always have: same 5 override sets, same activation semantics, same career gate (the KRILL button shows up once your VAB/SPH unlocks custom action groups). If you already know how to use stock action groups, you already know how to use KRILL. The same goes for controller axes: stock stops at four custom axis groups, KRILL keeps counting.

What it does

• Unlimited virtual action groups, on top of the stock 10 sparse by design (a group only exists once you actually assign something to it), with a visible-group cap you control from the difficulty settings page (20-99).
• Full symmetry with the 5 stock override sets (Default + 4): every extended group can be assigned differently per set, exactly like stock groups 1-10 already are.
• A single 3-column window (Action Groups | Parts | Actions), usable in the VAB/SPH and in flight: pick a group, pick a part, pick an action. No scrolling through six different screens.
• A global player keymap with "press it now" capture: click Capture, press the key or joystick button you want, done. Works with keyboard keys and joystick buttons interchangeably, including layered modifier combinations for extended groups.
• Non-blocking conflict warnings: if a key is already in use by another KRILL bind or by a stock keybind, you're told exactly what — nothing is ever silently overwritten or blocked.
• Jump directly to any set with its own dedicated key, independent of whichever set happens to be active right now (stock's F6/F7 only step through sets one at a time).
• A manual Trigger button, to fire a group instantly in flight without touching its key at all (useful for testing a setup before binding it).
• Three actuation kinds per extended group (per set): Pulse (default — fires once per press, like any stock group), Toggle (keeps a persisted on/off state you can also set by hand from the window, e.g. to resync after changing a part from its right-click menu) and Hold (active only while the key or the Trigger button is physically held, like stock's own Brakes).
• A clean on/off signal for other mods: every extended group presents a plain on/off level. A Pulse reads on for 750 ms after firing, a Toggle its state, a Hold whether it's held right now. Works through a public read API (KrillQuery.GetGroupState), so a mod like KRAB can use a KRILL group as an input without knowing anything about kinds. A per-group Info/Caution/Warning label is also stored for the future flight console.
• Groups 1-10 stay exactly where you already assign them (the stock Action Groups screen): KRILL only adds naming and rebinding for them, it never duplicates or replaces that screen.
• Extended axis groups (A5 and up), for anything on your controller that is an axis rather than a button: robotic servos, engine thrust limiters, control-surface authority, light intensity. Any part field stock lets you put on a custom axis. Same window, same "+ Part" gesture (only parts with axis fields are offered), a "+ Field" list per part, symmetry handled for you, everything per craft and per override set. Each assigned field has its own Normal/Inverted, Absolute/Incremental and speed (20-300 %/s) settings, the three options stock has, so one axis can drive several fields in different ways.
• Two axis kinds: Spring returns to a rest position (-1, 0 or +1) when you let go of the stick; Fixed stays where you left it and the value is saved with the craft, like a throttle lever. A live value slider in the window follows the controller, or lets you set the axis by hand when no channel is bound.
• +/- keys for extended axes (0.3.1), next to the controller channel, like stock's own custom axes have: a keyboard key or joystick button (modifiers allowed) captured from the axis footer. What a held key does depends on the kind: a Spring axis snaps to ±1 and springs back when released (an optional travel time in the settings turns the snap into a ramp), a Fixed axis moves at a configurable speed and stays put, a trim you can set from a hat switch. A held key wins over the channel; on release the channel takes over again.
• Axis capture with a "move it now" gesture, a global per-player axis map that survives Unity renumbering your joysticks, conflict warnings against every stock axis binding, and a global dead zone setting (default 5 %). Delete during any capture removes the bind.
• Stock custom axes 1-4 appear as rows A1-A4: rename them, capture their channel from the KRILL window (it writes stock's own binding and leaves inversion, sensitivity and dead zone to the stock Input screen), watch their live value.
• An analog signal for other mods to match the on/off one: KrillQuery.GetAxisState(vessel, axis) gives the current level (-1..1) of any axis, stock 1-4 included.
• Every assignment travels with the craft (save/load, docking/undocking, symmetry parts) the same way stock action-group data does; the player keymap itself is global, shared across every save and vessel.
• Localization: English and Italian, full parity (every player-facing string in both).

Requirements

• Kerbal Space Program 1.12.5
• ModuleManager
• ToolbarControl (adds the KRILL button to the stock toolbar / Blizzy's Toolbar)
• The stock "Action group sets" general setting (Advanced Settings → General → ADDITIONAL_ACTION_GROUPS) must be enabled for the 5-set system to be available at all.

Installation

Copy the contents of this repository into your GameData folder, so you end up with GameData/KRILL/.... Make sure ModuleManager and ToolbarControl are installed alongside it.

Configuring a HOTAS with a lot of buttons

KSP 1.12.x runs on Unity's legacy input system, which only recognizes 20 buttons per joystick device (and 20 axes per device, up to 11 devices — checked in the game's compiled input table). This is a Unity limitation, not a KSP or KRILL one. On a HOTAS with 60-100+ physical buttons across a stick, throttle, and extension modules, anything past button #20 on a given device is invisible to the game if bound as a native joystick button.

A few tested ways around it, using your device's own mapping software:

• Route extra buttons as keyboard emulation instead of native joystick buttons. Keyboard input draws from a much larger key pool, so this sidesteps the 20-button cap entirely. One caveat: Unity only exposes F1-F15 to KSP: the hidden Windows virtual keys F16-F24 exist at the OS level but have no Unity KeyCode, so they can't be bound in-game.
• Stack modifiers on an otherwise-unused key (Numpad digits are a good choice: stock KSP doesn't use them). Unity's input has no chord suppression, so Ctrl+Num1, Shift+Num1, Alt+Num1 and so on each fire independently as long as bare Num1 has no binding of its own... one bank of physical buttons multiplied by however many modifier combinations you use. Just watch out for Num Lock.
• Turn rotary encoders and other "analog-ish" controls into axes in the device's software and give them to KRILL's extended axes instead of consuming two buttons each (up/down). Twenty axes per device is a lot of room, and each encoder moved off the button table frees two of your twenty buttons.
• Layer a modifier chord onto an opposite-direction pair already in use (e.g. a chord that includes both W and S, already bound to pitch). Since W and S drive opposite directions on the same axis, holding both together cancels out to zero on that axis while the chord action still fires independently — a way to reclaim already-used keys instead of needing free ones. There can be a few milliseconds of asymmetric input before the cancellation lands, likely imperceptible under SAS but worth checking if you fly manually at high precision.

Known limitations & Future Plans

• English and Italian only. Contributions are welcome (I personally accept AI-assisted translation, as long as they are human-reviewed before issuing).
• Override sets (1-4) are renamed from stock's own UI, not from KRILL: the KRILL window shows the set names on its tabs but has no rename field of its own (stock has nowhere to store those names before a vessel exists anyway).
• No in-flight console (button grid) yet: activation is by keybind or from the KRILL window's own Trigger button.
• A Hold-kind group interrupted by a save (quicksave, or leaving to the Space Center while still pressing) reads as off after loading, but the part itself keeps whatever state the save captured (the same thing happens with stock's Brakes held through a quicksave). The next press resyncs it.
• No integration into the stock Action Groups app or the editor's Actions screen (yet?): extended groups and axes are managed entirely from KRILL's own window.
• The +/- keys of the stock custom axes A1-A4 are shown in the KRILL window but are still captured in stock's own Input settings screen: KRILL captures their channel, not (yet) their keys. There is no mouse-wheel "stepped" source for any axis.
• A Spring axis's live position is never saved: after a load it sits at its rest position until the stick moves. A Fixed axis's value is saved with the craft.
• While the mouse is over the KRILL window, stock's own custom axes 1-4 stop reading the controller (stock pauses them whenever a UI holds the input lock, its own Input screen included); KRILL's extended axes keep following.
• Not a KRILL bug, but easy to blame on it: in the stock editor's axis options, the speed slider can show absurd percentages (e.g. 66600 %) on systems whose locale uses a comma as decimal separator. Stock parses its own speed table with the system culture. KRILL's own speed steps are stored as numbers and are unaffected.

License

MIT.

Credits

Author: Rjoande. Built with the help of Claude Code.