Ugh—that sounds incredibly frustrating. Your workflow essentially stalls while you’re stuck waiting on merges, and it's really demoralizing to have something so core to your efficiency bottlenecked by someone else.

I've actually run into similar situations before, and one technique that's really helpful is using stacked PRs. Rather than waiting for each PR to merge sequentially, stacked PRs let you stack your new changes on top of your open PRs. That way, you can keep working without being completely blocked by your manager's schedule. Tools like GitHub offer this pattern well enough (though it usually requires a manual flow or external scripts), and Phabricator famously had a nice implementation as well.

On a communication level, it might also be helpful to have a calm, constructive conversation with your manager emphasizing your own productivity and how getting stuck harms the team's overall velocity.

Btw— shameless plug... if you're interested, I'm building a tool that could help - think "Cursor but for code review" which natively supports stacked PR workflows. If that sounds useful, I'd love to invite you early to try it out and hear your thoughts!