Symbol switches

Are those switches only for the screen they are on? Or can I place them through out a series of maps to open up a central passageway?

The switches are only for the screen they occupy. In fact, even if you clear the barrier it resets when you leave the screen. You could make a central barrier out of keys however, and require the player to enter code symbols on multiple screens to get the keys needed.

Or you could make very elaborate use of shifts and flags, but to be honest it's hardly worth the effort.

Or as I have done with a couple levels, make a "Maze" with these things and force plenty of save points and the up arrow levers.  Concept is basically put, make the player have to kill themselves after a save point activation, and that will reset the barriers.

Example?