To avoid campaign duplication that generates inconsistencies in mailbox interpretation, it is preferable to create templates of these campaigns used in order to resume on a clean basis.
To do this, you can retrieve the content of your campaign by duplicating it.

Then go to the "Message" tab and then to "advanced configurations".

At the bottom of the dropdown menu, you will be able to select "save as template".

This allows you to organize your templates and save them.