Being able to select the email Reply-To header as dynamic content would vastly simplify existing flows I have, as well as improving the robustness of the process.
The use case is typically that you have some kind of flow that fulfills a request on behalf of a user and then notify some other user(s). The recipients of the notification may want to follow up the original requester with some questions, then it is convenient to have a correctly set reply-to header so that reply is not sent to the shared inbox by accident. To avoid having to grant permissions on all possible mailboxes, you send from a shared mailbox.
I was about to use Power Automate to completed a business workflow but got stuck without Reply-To. None of the emailing options (Outlook, SendGrid, etc) seem to have this option.