Hello @user065195 ,
If you have the HTML of the template made on another platform, and know how to code, you could potentially utilize our custom code editor. Otherwise there isn't really anything that'd be able to bring over an email template from another source, and would require you to either remake it from scratch, or from a PDF version.
See also:
Creating a reusable master template for direct copying
Inserting an uploaded document into an email
... View more