Answers...

to commonly asked questions.

My notes are gone.

After I switched AppleID's, now my notes are gone. How can I get them back?
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I’m guessing you had notes that were associated with the other AppleID account. Should be a simple fix. We log into that account, pull those notes over to your current appleID notes account, then log back out again. You can use Internet accounts in system preferences to add the other iCloud. Account as a sub account. You will have less syncing options since you'll already have a primary iCloud account. So things like keychain, find my Mac, photos, will not be available to sync but notes will.

Then open notes and just drag the notes from the one account over to the other. Afterward, you can return to system preferences internet accounts pane and remove the sub iCloud account.
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