I know of Potent Magic. Any other systems that Shape and Materials fit into in any of the books?
Crafters with Touched by (Realm) can add S/M bonuses to their craft total.
Grugrach tattoos benefit from S/M bonuses.
They're important for Experimental Philosophy from Art & Academe. If you can eat an entire elephant tusk in a season, that's +5 to invent your Pharmaceutical Theriac that cures moderate to severe toe punctures!
Mechanicals/Rusticani can use them for Spell Foci.
Verditius magi can use shape bonuses for Items of Quality.
An Object of Virtue's bonus in a Form can provide Puissant Form. More generally the bonuses guide what Virtues you can get when enriching.
Wondrous Items from City and Guild.
The Major virtue Potent Sorcery (RM p.11) works roughly the same way as Potent Magic, but for Supernatural Abilities.
Not sure if Faith & Flame was published before or after Rival Magic but in said book Folk Witches utilize standard Potent Magic over Potent Sorcery.
Could be that much like the baseline Potent Magic theirs is reliant on the users' Magic Theory equivalent to determine the bonus gained, whereas Potent Sorcery always gives a maximum bonus.