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

Intuitive Illusions

FEAT 5
GNOME
Activity free action
Prerequisites Illusion Sense
Frequency once per day
Trigger Your turn begins.

Illusion magic comes to you so naturally that you can effortlessly sustain your magical ruses. You immediately gain the effects of a Sustain a Spell action to extend the duration of one of your active illusion spells.

Pathfinder Lost Omens Character GuideOGL