Can we create instance groups after-the-fact?

Using TM 2022. I brought in an .skp of a table lamp, the file consists of a parent folder containing 7 meshes. I added a light to this folder and then saved it as an object in my library.
I then added this lamp to 100 tables. By dragging it in from the library.
They are not instances. When I select the lamps and right click ‘new instance groups’ is greyed out. Is there a way for me to make them instances so I can control the lights simultaneously?
Or is the only answer to delete them all and put them back in using the SHIFT-drag method?