Thanks @uxamanda, that's excatly the workaround I meant. 
There's currently a small limitation within the App @laurent.
Plugin commands will only be shown in the keyboard shortcuts editor once they have shortcuts assigned. Whereby it doesn't matter whether the shortcuts are defined as default accelarators in the plugin's implementation or manually added to the keymaps-desktop.json.
I am not quite sure, but I seem to remember that the behavior only occurs when the commands are displayed in a submenu.