Not sure I understand. But likely yes
If you open 1 object in O2, Copy, close it.
Open another object in O2, paste. Bingo, merged.
Or simply use the "Merge" load functions.
1 trick to do before you "copy". Name EVERYTHING you are about to copy to something like "copy1"
That way if you want to move ONLY what you pasted or want to delete what you pasted, you just select the "copy1".