As a system field I am unable to set
CaseNumber on the default Case object when I do my imports from my legacy Org. I've already created a custom Permissions Set as per and In there I do see Edit Access column for Case Object but the checkbox is grayed out for Case Number.
Is there a way to allow setting that field, I would only need it allowed during an initial import to preserve the original case numbers as they're often quoted in emails and comments by my colleauges; which I've also migrated.
This is in Enterprise Edition.