alternate ligature anchors

If I want to place, say, a cedillacomb on the t for a ligature t_i that’s in a different place than bottom_1 what is the syntax? It looks like context anchors don’t work for ligatures, or I’d use something like *bottom_1.cedilla with lookupflag useMarkFilteringSet cedillacomb; * to just filter that one mark at that location. Or perhaps they do work and something is off with this OT entry?

If I use bottom_1.cedilla the preview window does show the cedilla at the secondary anchor, but when exporting still uses the standard bottom_1 anchor.

Thanks for any help!

The ligature anchors are not as well developed. I need to work on them a bit more.