xcape

https://forums.bunsenlabs.org/viewtopic.php?pid=66403

The idea is to patch ‘the usual’ openbox dual-key shortcuts to single key, examples (using stretchbang logic);

xcape -e 'Super_L=Super_L|space' &

will bring-up ob root menu on super-l release.

xcape -e 'Super_L=Alt_L|space' &

will run gmrun on super-l release.

You could put some of that in ob autostart.