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If I’m understanding your request correctly, you should be able to do this with the existing PR template feature. I’ve actually used this myself in some of my own projects to help guide reviewers on the steps they should take when going through my PRs.
The way that I do it, is to incorporate a checklist for reviewers into my PR template. So, whenever I open a PR, the checklist automatically populates in the PR body. I can then add any other instructions specific to that PR, if needed, and add the reviewers I need to take a look at the PR. Each reviewer will then be able to see the checklist and follow it to ensure they’ve taken all the steps I need them to to finish a review.
Is this what you’re looking for? If that’s not quite what you need, please do let me know a few more details and I’ll be sure to share it with the appropriate teams as a feature request.