Hello
I tried to place a large building from "Fortify" on my map with the help of the "RustEdit" software but it is really too slow to place. I will try to place it with this "Copy Past" mod but I guess the building will not be indestructible? Which would be annoying since he must serve in a pvp zone.

you could create a zone around it with zone manager to make it indestructable. That is what I do with the town I paste in but you of course have to repeat it every wipe.