For now - this is my workaround:
- Install Mosaico Message Templates
- Go to Message Templates, since the edit option is disabled, copy the link to edit one of the other templates and edit the ID in the URL to another number (usually larger, mine was only 6 away), until you discover the template you want to edit.
- Do not make edits there, instead copy the message body, go back to message templates, create a new template and then paste the message body into the new template.
- add your tokens, make any changes you need, save and then you should be good to go!
There must be an easier way, but at-least this worked for me. When I just tried to do it using the template that mosaico message templates generates, i would get smarty errors.