the „official“ way is to use a conditional activation group that is only true if the menu is either currently hovered
hovered_floating_menu_identifier == "thenameofyourmenu"
Or is only active if the menu is currently visible
visible_floating_menu_identifiers CONTAINS "thenameofyourmenu"
Then you can use any trigger (including keyboard shortcuts) combined with the predefined action "Execute Actions For Configured Trigger". A floating menu item is also a configured trigger, thus will execute it's actions when called like this
(or use named triggers or directly assign the action you want to execute)