How can I re-add the gap above the tabs when in full screen mode (OS X)
A previous version of firefox added a little gap above the tabs when in full screen mode. This prevented the toolbar from appearing when moving the cursor over the tabs. However, in recent versions, this "gap" has been removed. So now, when I try to change tabs my moving my mouse to the top of the screen, the menu bar appears, delaying the process of changing tabs.
It's really annoying - I don't know why this feature was removed.
(This may be particular to firefox on OS X)
What you could to is to put the tabs on the bottom instead of "on top" which is the default value. This way, your tabs will stay below the location bar.
Please see this article: https://support.mozilla.org/en-US/kb/put-tabs-back-on-bottom
You can also use key shortcuts to switch between tabs quickly: