After make modification save file in /usr/share/enigma2/keymap.usr. Then in /etc/enigma/settings set this config.usage.keymap=/usr/share/enigma2/keymap.usr. Dont know if there is GUI for this settings in BH or OBHIt's probably a little bit exaggerated to modify keymap to perform this action. I'd rather use the plugin Quickbutton (not to be mistaken with Multiquickbutton).
Instead, I edited keymap to get rid of the annoying strange assignment to P+/P- to bouquets (that I find very, very uncomfy and annoying) and I swapped its assignment to LEFT/RIGHT, although after every software update I have to replace again my keymap because the update replaces mine with the original.