When source files have been merged during project set-up, it seems it is not possible to open multiple merged files at the same time in Studio. So, for example, after merging 20 files into Part 1.sdlxliff with 10 files and part 2.sdlxliff with 10 files, we cannot open the 2 merged files at the same time (e.g. for preparation, translation or review).
So it would be handy to be able to open multiple merged files at the same time.