The Booster Refueler is a module of the Boosting locomotion; it provides a particular functionality for its parent Booster. If it is disabled or removed, then the relevant boosting functionality will behave as by default. Most modules can optionally affect change globally (for both hands' Boosters). Booster modules can also depend upon conditions specified by their dependencies settings.
The Refueler is responsible for produce fuel force to restore (add without going past the maximum) fuel force to the Fuel Supply. Refueling can be toggled and the amount of fuel force by which to refuel can be tweaked.