Is it possible to pre fill the email template/message when opening a new email? I open a new email window with

window.open()

and pre fill the entity and that works fine. But when setting the template, the template field does get filled but the message itself doesn't and the template field becomes inline. Is there a way to pass in the template so the subject and message fields get filled with the contents of the template? Preferably without deploying a script on the message record