Truncate undo list

If one has an undo list, is there a way to
capture its its given state/length,
make additional edits, and then go back to
its captured state/length (with or without backing
out any new changes) and remove all later members of
the undo list (no redos) - truncate the undo list.

Thanks
Richard

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Quis custodiet ipsos custodes

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