How to edit linked source collection after make local all?


I have a project which involves an IFC (BIM) model from customer. This was converted to blender using 2.79 and is used as the master file.

I also have several rooms done in Solidworks which is exported to STL, cleaned up in Blender and added to the 2.80 master file using file/link. I believe instance collection was checked. I could now go into these linked files and turn on or off whatever I want (such as reference walls and other guide geometry).

Then I do Object/Relations/Make Local/All.
Within Blenderfile/objects, I can only access the full collection, and do basic move and rotate stuff but no editing. Can’t see the object the collection consist of.
Within BlenderFile/collections, I can see everything within the collections, but I can’t access any editing.

So now the question is, how do I edit previously linked collections now made local, and the objects in them?

I can’t share the file, unfortunately. (2100 objects, 5mill faces, customer and our private data).