Moving to Monterey: Mail

I have been moving to Monterey from High Sierra, and exporting my email boxes (got some) for importing to the new Mail on Monterey.

I have creating first the mail box account

Then importing the correspondent mailbox, which creates and import tag on Mail with inbox, sent and deleted sub-tags

Then I copy (move) all the mails from import/inbox tag into the Mailbox created

Then I set all the mails as read

It seems been working even though it takes long time to complete a single mailbox; however I could handle it.

I have actually an issue, when I create a new mailbox, Mail creates an inbox under Favourites tag and anther identical inbox tag below under the name of the Mailbox. It was not like this in the High Sierra version. If I delete the second inbox tag, it deletes all the mails in both inbox tags. How could I delete the second inbox tag?