It was this: Wish: Add mask and other via settings to individual via (lp:#1778887) (#2163) · Issues · KiCad / KiCad Source Code / kicad · GitLab, through the link “closing in favour of…”
If someone needs via mask options and wants to remind developers about that, they can go to the main issue and add a comment there to make that detail explicit.
If our chain of interpretation eepete->SembazuruCDE->eelik is correct, we are talking about “keepout areas” in footprints so that you can keep tracks and zones out of an area in a footprint.
That has been implemented already, see Post-v5 new features and development news - #107 by eelik..