could a (default or optional) shortcut key for that menu to open be put in place? I had in mind the alt key, from using firefox, which hides and closes the toolbar,
You can right-click on the plasmoid, go to settings, go to the "Keyboard Shortcuts" pane, and set a shortcut.
apologies, I should have specified, the menu I was mentioning was the global shortcut "hamburger" shortcut/window decoration, is there a way to give that a shortcut key?