How can I set Firefox to respect my custom Mac keyboard shortcuts? In System Preferences, I have ⌘D set to Enter Full Screen and Exit Full Screen. I have been using these shortcuts for close to a decade now, and I'm really not interested in relearning them.



Unfortunately, ⌘D is also Firefox's built-in shortcut for creating a new bookmark. Unlike most Mac apps I've used, Firefox's built-in shortcut appears to take precedence over my custom one.

How can I make Firefox to respect my ⌘D shortcut for entering and exiting fullscreen?

(Small note: I happen to be on a very old version of macOS, specifically 10.9 Mavericks. I don't think this is relevant to the question.)
Unfortunately, this is a long-running, documented bug in Firefox. https://bugzilla.mozilla.org/show_bug.cgi?id=1333781
You can add custom keyboard shortcuts which Firefox does not already use, but you cannot remap a shortcut that is built into Firefox.