Restrict 'Open Quickly's scope to currently open project in Xcode?
Quick open lost its value to me. What you can do until the bug is fixed / scope can be specified:
Use: Cmd + Shift + J
Then type the file you want to 'Quick open'. This is restricted to the files in the project Navigator.
I suspect that the scope is based on which navigator is currently chosen. When I start getting weird results, I go select the project navigator, then try again and get the results I expected.