When you open an email by doing double click on it, I would like to know is the top panel of the email (header - indicate in the screenshot with a blue rectangle -) can be customized by adding text or other controls. Also in the context menu that appears when you click on the three dots button, I would like to know if I can add some options there. If that possible. Below I attach a screenshot and I indicate there the places where I would like to place these things (see blue arrows).
Also I would like to do the same in the preview area where the mail is shown when you select it from the messages list.