Boost an existing reel/post directly into a click-to-WhatsApp ad

Right now I can create a click-to-WhatsApp (CTWA) ad in Zernio, but only by building a brand new creative from scratch. I can't take an already-published Instagram/Facebook reel or post and turn it into a click-to-WhatsApp ad. Boost has no WhatsApp CTA option, and the CTWA/messaging ad endpoint doesn't accept an existing post/reel ID.

What I'd like: the ability to reuse an existing post/reel as the creative for a click-to-WhatsApp ad, either as a WhatsApp CTA option on Boost, or by passing an existing post/reel ID (object_story_id) into the CTWA/messaging ad flow.

Why it matters: reusing a reel that already has organic engagement keeps that social proof (likes/comments/views) instead of starting a fresh creative from zero, which usually performs better and saves setup time.