When I move objects into a collection by drag and drop, or by M key, it does not move the whole structure. I tried Select Hierarchy, but there are still objects left, and I am not sure how to remove it. I tried to search but without any success.
I would like to move it into collections to do a cleanup and make it easier to use.
It seems like a duplication, but if I remove the item in the root it deletes it in the collection as well. I tried to click on Unlink but it deletes it.