One-to-many substitutions?

So I’m aware of how to make many-to-one substitutions by typing something like:

sub a’ n’ d’ by and.alt;

But is there a way to do a one-to-many substitution? I figure it could be a good way to reuse assets from different glyphs and reduce redundancies, particularly in ornamental fonts.

You don’t need contextual tick marks in this case. This suffices:

sub a n d by a_n_d.alt;

One-to-many substitutions work exactly the other way around. Just keep in mind that not every renderer supports them fully for Latin. InDesign has difficulties, for instance.