The gender transition leader, the HR person who is placed in charge of a gender transition, should solicit a short letter from management expressing management support. Most likely, management is going to ask HR to draft the letter, since they expect that HR knows what to say more than they do. Of course, there is no reason why HR should be an expert on the subject, but that’s what managers often do. What should such a letter say?
See a template for a management letter regarding transgender transition here