If you're having issues executing shell_command maps but your karaml map looks correct (and you confirmed this isn't a bug in karaml itself by checking it was translated correctly intokarabiner.json) try executing the following in your terminal:

launchctl kickstart -k gui/$(id -u)/org.pqrs.karabiner.karabiner_console_user_server

This will restart the Karabiner-Elements Console User Server launchd job for the current user.

I need to do this on occasion after using my quick-symbols layer (for ⌘⌃⇧⌥ etc). Have not been able to figure out why this happens. No results for the relevant error message in KE's issues:

[2023-04-19 20:46:20.361] [error] [console_user_server] shell_command stderr:execution error: Can’t make some data into the expected type. (-1700)

See #2 (comment)