Perfect, thank you! :)
Display in use is a standard Reprap Discounts Full Graphics one (on a Wanhao DI3). FEATURE_CONTROLLER 11 (ui.h: Line 630)
The only functions using UI_RESET_PIN are:
UI_KEYS_INIT_BUTTON_LOW(UI_RESET_PIN); // Kill pin
on line 843 and
UI_KEYS_BUTTON_LOW(UI_RESET_PIN,UI_ACTION_RESET);
on line 847. Which both should do nothing with "-1" as argument (at least PINMODE(-1,INPUT); and so on do nothing to my understanding). I'll try with and without commenting the two functions out.
Thanks again!