An update, for those who might still be trying to migrate Stickies from something as old as a 2011 MBP with High Sierra to an M1 MBA with Big Sur. I set this new machine up fresh and have been manually migrating stuff as needed. You may be surprised just how much digital rubbish you can collect in 10 years.
What ended up working for me was to simply copy the StickiesDatabase from /Library on the old Mac to the same location on the new Mac. With Stickies closed, I then went to Library/Containers/Stickies on the new Mac and deleted that, as well as Library/Containers/com.apple.StickiesMigration. Yes, I had already opened Stickies, found nothing, then decided I wanted to bring my old ones over.
When I opened Stickies again, the folder at Library/Containers/Stickies and Library/Containers/com.apple.StickiesMigration had been re-created and all my old Stickies appeared, all stacked on top of each other. Just drag them off one by one and expand as required. You can now delete the StickiesDatabase file from /Library as Big Sur doesn't need that going forward. All your Stickie data is now in Library/Containers/Stickies
As always, be sure things are working as desired
before you empty the trash. TM Backups are also a very good idea.
- "Locate and Delete these 2 folders in Catalina (Hidden) user library, ~/Library/Containers/com.apple.Stickies and ~/Library/Containers/com.apple.Stickies.migrated" - These 2 folders don't seem to exist at all in Big Sur, at least I haven't seen them, before and after the manual migration of the old stickies.
- "Do not delete, ~/Library/Containers/com.apple.Stickies.migration this folder is needed for importing the old data." - I did delete it, together with Library/Containers/Stickies, but both were re-created when I opened Stickies again. No computer restart required. I think the migration folder is only for when upgrading the OS on a machine with existing stickies, not when manually transferring stickies from another computer. I can now see all the stickies in Library/Containers/Stickies/Data/Library/Stickies.