What can you do with the heart icon if there's no favorites functionality??? LOL
Anyway - I know there's the modification vBFavorites as shared by Psionic Vision ==>
https://vborg.vbsupport.ru/showthread.php?t=215197 -- It's a 3.8.x modification, I'm not totally sure if it has been updated to work with the vB 4.x series though.... That might be a good place to start
HTH,
J.