Yes! Someone has to make the glyphs and someone has to write the rules that say "unconditionally replace this sequence of glyphs with this glyph" or "in this context, replace this glyph with that one" and so on. The only thing the editor has to do is decide to use them.

They're usually grouped into features: standard ligatures (liga), discretionary ligatures (dlig), historical ligatures (hlig), contextual ligatures (clig), and so on. OpenType fonts can also provide stylistic sets, which might swap out some glyphs with alternatives.