This might seem live a silly suggestion, but isn't a web browser a GUI.
Let's look at this for a moment:
GUI: Graphical User Interface,
generally means you use a mouse and keyboard to effect the use of the system.
Server Manager is loaded through a Web Browser, with links that you click on with the mouse, buttons, drop downs, etc to change settings and then you click the save button to make the changes.
What the &*(^ else do you want?