How do I replace i and j with dotless i and j when combining with diacrtics?

I use FontForge. I’ve seen (via the key metrics window) that some fonts ditch the dot above the i and j by replacing them with their dotless counterparts when combining them diacritics like grave and acute. But for my font, I haven’t been able to achieve so. PLEASE IT’S URGENT AF. Quick responses appreciated.

[EDIT] I think it has something to do with chaining substitution or so.

Please read this tutorial:

You would do it in ccmp. Glyphs does it automatically if you have i, j, idotless, jdotless, and combining marks (e.g. acutecomb) in your font.

As much as I’d love to use Glyphs, I unfortunately am on a Windows (or not so unfortunately) and I’m only considering free options. Any experience with the likes of fontforge?

Then you might need to ask on the fontforge forum? One reasons we can provide support for our customers is because they have payed for it.