In batclient, the main menu can be accessed with at least pressing ESC or
right-clickin the batclient desktop. If firefox or chrome would operate with
same logic, they would be a bit more harder to use but fortunately they both
have been wise enough to add a button which you can use to access the menu.
Some kind of button should be added to batclient too, maybe even a whole menu
system similar to firefox could be added and include all the subwindow options
too.