I have a master file that has a “Master Block” inserted as a linked reference block. If this Mater Block contains “Block A” and I try to insert Block A as a linked reference block into the master file it will let me drop a block instance but I won’t be able to interact with it in any way, and it will not show up in the block manager. If I save, close the master file, and reopen the block instance will be gone.
This is similar behavior to what would happen in rhino 7 if you tried to link a block twice.