The code in gnc_gui_init in src/gnume-utils/gnc-gnome-utils.c has an ifdef that causes it to load the accelerator key map from osx_accel_map in the Gnucash package but the code in code in gnc_gui_shutdown in the same file doesn't.  Thus it saves the (possibly modified) accelerator map in ~/Library/Application Support/Gnucash/accelerator-map.  This file is ignored, but will be overwritten with the defaults from osx_accel_map the next time Gnucash is run.  It seems like gnc_gui_init should first load osx_accel_map from the package and then load ~/Library/Application Support/Gnucash/accelerator-map.  Or perhaps it should load ~/Library/Application Support/Gnucash/accelerator-map if it exists and load osx_accel_map only if accelerator-map doesn't exist.  Or a third alternative is to load osx_accel_map in gnc_gui_init and don't save anything anywhere in gnc_gui_shutdown in the Mac version.  I don't know which option would be best since I don't use this version of Gnucash.