I took a look into "src/widgets/widget-sizes.h" and trying to change these values but even after a clean build it does not seems to have any effect :
#define AUX_SPINBUTTON_WIDTH 

#define AUX_SPINBUTTON_WIDTH_SMALL 

#define AUX_OPTION_MENU_WIDTH 

#define AUX_MENU_ITEM_WIDT