Select Rename Tag, then click Rename to confirm. The tag is updated in all notes and Smart Folders that use it.
Tip: You can rename a tag to a name that’s already in your Tag Browser. This can be useful if you want to group together notes that have similar tags, such as #house and #home.
If you rename a tag in a shared note, it appears as dimmed text to other participants who don’t have the tag in their Tag Browser. They can Control-click the tag, then choose Add to Tags.
In the Notes app Sort and pin notes on Mac