I am a complete font newbie, but looking at the standard (https://www.iso.org/standard/66391.html https://www.iso.org/standard/66391.html), it seems like there

I am a complete font newbie, but looking at the standard (https://www.iso.org/standard/66391.html https://www.iso.org/standard/66391.html), it seems like there exists a feature called "contextual glyphs", which means you can supply alternative glyphs (like ligatures) given a particular sequence of glyphs. I imagine you could crack open the font file itself and find out how this works - I'm not familiar with any of the tools to do this though. Here's (I think) more detail: https://fontforge.github.io/editexample6-5.html https://fontforge.github.io/editexample6-5.html