I would like to have the possibility of having access to the headers of the email as the Dynamic Content. While my particular need is to use the Message-Id email header (which is different from the Message Id dynamic content item), I would generalize this idea to add a new Dynamic Content item called Email Header, in which the user could enter the name of the header. I understand this would mean a slight modification in the Dynamic Content functionality, as this doesn't allow user's input at the moment.
My use case: when creating the tasks in Todoist from selected emails, I would like to add a link into the task description. This would allow me to open the email in question in the email client (Airmail) directly from the task in Todoist. The email client uses the Message-Id header to identify the message.