Your comments

I'm a huge user of the two group layout and really wish this behavior (only open a file once among all groups) was the default or at least configurable. When you have multiple groups with 10+ tabs each I'm constantly accidentalliy re-opening the same file in a different group because searching for an existing tab (that I don't remember is already open or not) is too slow.

I understand that you need to allow people to somehow still open the same file in a different group, but that could instead be done by a right -context menu or some kind of "split" command.