Opentype subtitution many by many (different number)

Hi!
It is a Opentype question which is not related to Glyphs app. Do you know if it is possible to substitute for example two glyphs by three glyphs?
I have managed to change one by multiple or multiple by multiple as long as are equal numbers (for example three by three).
Best regards,

Two possible ways:

  1. Two separate substitution lookups: first a ligature, a b to a_b, then a one-to-many lookup, a_b to a b c.
  2. A chaining contextual lookup, in which you call a lookup with one-to-many substitutions like sub x y' lookup ONE2MANY; and the lookup ONE2MANY is defined in the prefix and contains subs like sub y by y z;.

Thanks! it’s not ideal but I will manage with the first option.