A refresh started without this is how a week of unreleased configuration disappears. The checklist is short and every line is there because somebody lost something.
EXPORT FIRST. Configuration built in the target since the last refresh, as a configuration package. List the settings that packages do NOT capture — Lesson 5 — and record them by hand. Take a note of role assignments made in the target, which will be replaced by production's.
TELL PEOPLE, AND TELL THEM WHAT THEY LOSE. Everybody with work in that environment: testers mid-cycle, anybody holding an open sandbox, anybody whose test data is about to vanish. "The environment will be refreshed on Saturday" is not enough — say "anything you have built or entered there since the last refresh will be gone", because that is the sentence that makes people act.
VERIFY BEFORE, NOT AFTER. Confirm the export completed and can be opened. An export nobody checked is a backup nobody has, and this file records that lesson in the ops layer as well.
And agree the AFTER list before you start: who masks the data, who repoints the integrations, who reapplies the manual settings, and by when. The refresh itself takes hours and the post-work takes longer — and an environment that is refreshed but not yet masked or isolated is more dangerous than one that was never refreshed at all.
Write it once per estate and reuse it. This checklist is the same every time, and the only thing that changes is what the target holds.