Oh-my! No wonder I couldn’t figure it out. Thank you @saqimtiaz !
There may be a simpler solution depending on what the actual use case is.
The background is this idea, i.e I want to list all tiddlers that are part of the Controlpanel UI (a.k.a “settings”) so that end-users can manipulate them / the controlpanel UI more easily. Mario points to the prefix[$:/config] tiddlers and I figure that just maybe the the desired “settings tiddlers list” is the same as the tiddlers where those config tiddlers are mentioned. (BTW, if you have any immediate thoughts on this, they’d be welcome )