When adding content on Composer, there isn't an easy Email option to hyperlink. I think an element, such as the hyperlink options in eNotify, that allows the user to enter the email address and subject line would be incredibly helpful.
You can do this if you are using the CK Editor in Composer (the most recent editor we have available). You can select the test you would like to link the email to, then hit the link option. Enter the desired email address in the URL/Email field:
You should then see that the result is a "mailto" link that would function to open up an email in the user's default email client with a target of email@example.com (at least for this example). It doesn't set the subject as you described, but you can add that into the link and that can work as well. Here's some info on that: https://www.rapidtables.com/web/html/mailto.html. It would be nice to add those fields so they are a little easier so you don't have to worry about encoding the HTML etc. We'll get an enhancement request logged for that.
Let me know if that doesn't seem to help get the results you are looking for.
All the best,
You won't be notified about changes to this idea.