Enabling sign language interpretation in EXISTING recurring meeting

It took some doing, but I finally found out how to enable sign language interpretation for the account, and schedule and start a meeting with interpretation enabled. [It's stated, but I missed it at first: Must schedule and start from web portal.]

But we have existing recurring meetings which we'd like to provide interpretation for. Changing the meeting ID would be a big deal, essentially impossible. Is there any way to enable interpretation?