So, The weirdest thing happened to me...
I got a problem with not being able to option click a source file to open it next to the source file I'm working on.
Weird.... So, I booted back into my pre-catalina OS, and tested there. Option click works there.
So, back to Catalina beta. Created a new user account. Switched to that account, started xcode, created a new project and voila. Option click works. I thought I knew the fix: Use the new user account and work from there. So I open the project I was working on and...... No more option click to open a source file next to another source file.
So, on the same machine, same partition, same XCode, same XCode settings (!!!), I can use option clicking in projectONE on source files to open them next to the active editor, but not on projectTWO.
What could be the problem?
You probably already figured it out, but when it was happening to me it turned out I had split view editors with one of the editors being in focused mode (top-left corner arrows icon), so I couldn't see the other one. In that mode option-click doesn't do anything.
Thank you!!! Hunting down this issue was driving me mad!