Question - Cross Hotbar "Hide but Active" Option?

[Niwashi]

Is there away to lock or remove bar 3 while still being able to use it as cross hotbar?

Under Character Configuration --> Hotbar Settings --> Custom, you could set it as your expanded hotbar by setting L2->R2 and R2->L2 to its left and right sides respectively. Then just below that, under the "Set Selection" heading, remove crossbar 3 from the list of crossbars to cycle between (since you'll now have a different way to get to it).

With that set up, pressing just one of the controller's trigger buttons will activate your main crossbar as usual, but pressing both together will bring up your expanded bar instead. The order in which you press them determines which side of the expanded crossbar you get.

In much the same way, you can also set up one of your crossbars (called WXHB for no reason I can figure out) to activate on a double press of one of the trigger buttons. (Personally though, I find the double press a bit too finicky for combat actions, so I just use that one for out-of-combat stuff. YMMV)