the ▤ Menu key is just fantastic. Now, in Firefox, you can press 【▤ Menu c】 to copy, and 【▤ Menu p】 to paste. Also works in terminal and most other apps.
In desktop (file manager), you can press 【▤ Menu r】 to rename, 【▤ Menu d】 to delete, 【▤ Menu p】 to show info/properties, etc.
this is particularly nice when your keyboard has a nice positioned ▤ Menu key. For me, on the Truly Ergonomic Keyboard, that's the left space bar.
or, you can make your Caps Lock to be the ▤ Menu key.
xmodmap. 〔➤ Linux: xmodmap Tutorial ⌨〕.
In Linux GNU emacs, by default, pressing ▤ Menu key invokes “execute-extended-command” (M-x). (on Windows, you can set it so. See: Emacs: Add Custom Keys to Enhance Productivity.) Even better is to set ▤ Menu key as the lead key of key sequences for emacs's hundreds of commands. 〔➤ Banish Key Chords〕
when you buy a keyboard, never get one that has Fn key in place of ▤ Menu key. Because, the Fn key is hardwired, you cannot remap in OS. If you don't like its preset multimedia functions, it becomes a useless key on one of the most important spot. Like, a dead horse squatting in front yard.