Swing? If you're looking for a solution for your scenario where some user can modify component X and some other user can't, then threads are absolutely not part of that solution. All access to GUI components run on the same thread, that's a key part of Swing.
I assume your scenario looks something like this:
Customer is sitting (or standing) next to a screen choosing items to order. At some point customer likes the item but not the price, so he calls over Pat (the boss) who can change the price.
So what I would imagine after that is, Pat clicks on the "Super Signon" button and enters their password. Then changes the price, then clicks on the "Super Signoff" button, and the customer carries on from there.
Am I way off from what you were thinking? I don't see how you could possibly bring threads into that scenario even if you tried.