pf2e.fyi
From Pathfinder Lost Omens Pathfinder Society Guide, which isn't enabled.

Communal Sustain

FEAT 12
ARCHETYPE
Activity 1 action
Archetype Spellmaster
Prerequisites Spellmaster Dedication
Frequency once per round

Choose one spell with a sustained duration that one of your allies has in effect. You must be within 30 feet of the chosen ally. The ally can Sustain the Spell once as a free action, triggered at the start of their next turn.

Pathfinder Lost Omens Pathfinder Society GuideOGL