An interesting review of Otter loss-of-control accidents:
https://www.aviationlawgroup.com/ott...tch-movements/
The article states that the elevator tabs are servo tabs.
I've found a copy of the POH online and it confirms Megan's observation that the left "trim" tab is adjusted during flap selection. The POH does not specifically mention that the tabs are servo tabs, except in a "walk-around" illustration.
https://www.manualslib.com/manual/12...c-3-Otter.html