My first reaction was to say no, don't retire working code. And I think some people use
add-editor, even though it's fairly unworkable for me personally. My second thought was to realize that there could be a change to a future version of Qt that makes the code stop working. Who is going to want to maintain that? So now I lean towards removing it. Is there a way the removal can be scheduled for a future release, and a deprecation warning given in the meantime?
I wonder if leoJS has the add-editor command working. I imagine that it would not be hard to recreate Freewin in leoJS, and I think it would be worth doing once the plugin mechanism is working.