Each attitude control input (the WASD keys) moves the controls by a small amount and the controls do not return to neutral when released. Works kind of like trim, but more adjustable and easier to work with. May be familiar to players of the Microsoft Flight Simulator series.
Fully adjustable: easy to change the amount the controls move per key press.
Immediately center the controls by pressing Z.
Toggle on/off whenever desired by pressing Alt+Z.
Displays a small window showing the current control positions, along with the configurable settings.
The window can be shown or hidden by clicking the button in the stock toolbar.
Configurable settings:
Speed: how fast the controls move while pressing the key
Step: the minimum amount the controls are moved per key press. It also snaps the controls to multiples of this value, so larger values cause it to change in large discreet steps.
PrecisionControlsModifier: scales both Speed and Step by this amount when "precision controls" is turned on (the Caps Lock key in KSP's default key bindings).
ZeroControlsKey: the key bound to zeroing the controls. The default is 'z'. Note that toggling on/off is always Alt plus this key