Under "Edit Authorization Policy" currently you can forward basic user credentials and additionally "send domain in basic authentication." However the domain is always based on the URL. It would be very helpful to have a text-box where you could enter an arbitrary domain name.
Currently it supports either sending "username" or "URL-domain\username" if the "Send Domain in basic Authentication" is selected. It would be very helpful to instead of automatically filling in the URL domain to have a text-box that I could supply the domain name. i.e. "MYDOMAIN\username" where you enter "MYDOMAIN" in the text-box under "Edit Authorization Policy" for the domain to send.