I set up a template with "boilerplate" beneath the text area - more info than just a signature. Then I tried to open the saved template to write a message in it. I couldn't enter any text. Why have a template if it can't be used (edited before sending).

Also, your categories of Help exclude one very important category: "Using Thunderbird". I've used at least 6 major email programs in the last decade and they all cover the basics of using the application. I'm stunned that Thunderbird missed this completely. General Help on using templates would have circumvented the need for this question. Otherwise, I like it!