Compose an Email with a Selected Email address in Apple Mail App
What is shown in the top part of the Mail app can be customised



Click on the box I highlighted and choose Customise. You will get a list of fields to show.

One of them is the From fields which is the one you want. Strictly with well behaved mail clients and users the Reply-To is really more relevant as that is the one a reply will be sent to However I find that some correspondants don't use it - I don't know why.