Once you've formatted an email to your liking, you can duplicate it (i.e. copy it) and use it as a base for a new email. This technique is recommended if you've already sent the existing email, because contacts can only be sent the same email once by default.
How to duplicate an email
In any Journey, follow the steps below:
As demonstrated in the video, we strongly recommend giving the duplicated email a unique name and subject line (in addition to your content changes to the body of the email).
If you're using the Advanced Editor, you can also save emails as templates. Learn more here.