Continue Button Workaround?

One thing worth flagging before the workaround hunt: the browser autoplay setting you changed is local to your machine. Most learners' browsers block unmuted autoplay by default, so the clips that work great for you will likely sit silent (or behave inconsistently) for everyone else. Autoplay is a losing battle in the wild.

The pattern I'd build on instead: gate every clip behind a tap. One Storyline block per clip, video set to not autoplay, with a plain Play button the learner clicks. Nothing can stack or double-play, on first visit or on revisit, because nothing plays until the learner starts it — no autoplay flags, no Continue-button gymnastics. It also survives the LMS, where autoplay is almost always blocked.

You already found the answer on the Continue button: it disappears by design once clicked (it marks progress), so any solution that depends on it sticking around will break on revisit. And you're right that Button blocks can only jump to lessons, not blocks — so within-lesson gating has to come from click-to-play, not navigation.

If you want to stay 100% native in Rise, one clip per lesson is the only clean option, which you've ruled out. The Storyline-block-per-clip route is the one I'd ship.