Desideratus

That's one complex hotbutton window. You shouldn't have any problem copying mana from the player window to it - but don't disable it in your player window, as the existence of those screen pieces in the player window are some of the things the game checks for before issuing its "not compatible" red text message. The important thing to remember is to add a unique identifier to the names and screen ids of the pieces in the hotbutton window - the UI parser will only allow each unique name to be defined once.

The player window has some hard coded functionality that you won't be able to see if you do get this working though ... such as the in-combat indicator, the out of combat timer and combat state icon, and player roles.