FCPX Three screens won't let me choose my left screen?

Please begin by clarifying exactly what you mean by “editing” and “media”.

In the following I will explain explain how to achieve what I think that you meant, but maybe I am misunderstanding. I am thinking that you want the main FCP interface to be on the center screen and the browser on the left screen.

Here is how you achieve this.

1) In System Settings->Displays, click “Arrangement”. Drag the little white representation of the menu bar over to the left screen.

2) Start FCP on the center screen (*)

3) Window->Show in Second Display->Browsers

Done.

(*) there are several ways to do this step: you can just start it and if necessary drag the FCP window over; you can first click the menu bar to make this the “active screen” and launch FCP from Spotlight (my favorite); and you can even assign FCP to the center display.

You misunderstood me. I never meant for you to drag the screens, ONLY the little menubarlet.

Make sure that the screens are arranged according to how they are physically positioned - which I am sure they were before. If you changed them, and they are now out of order, reset this screen to match the real displays on your office.

It is not a problem to just drag Final Cut Pro to wherever you want it. If it starts on the wrong display, just drag.

If you want the full Final Cut Pro interface on only one of the displays, you don't need to do anything else.

Bur I was thinking that you wanted to do this:

in order to have the "files" on the left and the main FCP interface (including the viewer and timeline) in the center.

I am not sure if that is what you wanted, e.g. something like this:

Or maybe the viewers on the left and the rest on the center.

If you wanted something like this, then follow my previous instructions.

To clarify, step 1 is THIS: