Tab order in edit window
I have no idea what you mean. I think a screenshot would mean the world.
Start editing. Then press tab key. Focus and cursor should be moved into Summary field. Work in case of LiqudThreads. In regular edit window focus came to Cancel, Help and special symbols area.
If you don't mean the translation dialog from Translate extension, this is a bug in MediaWiki and should be reported on the bugzilla.