Prior to Xcode 11, you could use cmd+shift+o
to open the quick open menu, and then use opt+shift+enter
to show the little jump dialog to decide where to open the file, e.g.
Note that the dialog has spots for opening in new window or new tab.
In XCode 11, with all the editor improvements (which are awesome), the little jump dialog has been replaced with some blue highlights that show up in the current window. This seems nice, but I can't figure out how to get a file to open in a new tab or new window.
Didn't realize how important this was in my workflow until it went away :)