[Therion] How to do better join from scraps in different .th2 files?

I have to join scraps in different .th2 files. The semi-automatic join doesn’t do a good job. I need to redraw the scraps wall near the join to do a better work. Can I insert in the Xtherion map editor a scrap from another .th2 file in the background to do a better position of the scrap walls to can produce better scraps joins? Evaristo Quiroga