Thank you for your answer. So I installed the 4.27 version and I could not find the options you mentioned in Convert to Static Mesh until I saw, a bit bellow in the Rick Click Panel “Merge Actor”.
So actually, I should not use Right Click ->Convert to Static Mesh, but rather:
Right Click → Merge Actor, ( I had no idea this option existed), because this one keeps the collision while the first…
Well, I don’t get the point of the “Convert To Static Mesh” anymore since I’ve discovered Merge Actor. It looks like Merge Actor is actually a Convert to Static Mesh, but way way better.