(Easy 6.1 / same problem with Fossapup ( but briefly tested in Fossapup) )
I created a keyboard shorcut in JWM for showdesktop (Alt + z)
After relaunch of JWM, the shorcut works. But after a reboot (or a relaunch of X) the shorcut does not work until JWM is relaunched.
I tested with direct edit of /root/.jwmrc, direct edit of /root/.jwm/jwmrc-personal or with EasyJWM in Easy 6.1 (Tested with direct edit in Fossapup)
(EDIT : fix the name of the file .jwmrc)