Since mytokens can't be accessed in the Design Studio (they're in Marketing Activities), is there a best practice for creating and managing email templates that use mytokens?
Yup - I have them there.
What's the method for creating email templates in the Design Studio with mytokens? Do I manually enter them rather than choosing from the token select list? Or do I save an email with mytokens as a template when I'm in Marketing Activities?
That's a drag - so you have to manually copy/paste (or type) the mytoken code into the email template within the design studio.