Shows the running game inside a pane of the 3D editor's split viewport instead of the separate Game tab. Tick "Game Window" on any pane; Play lands the game there, Stop hands the pane back. Auto-creates a second viewport, docks the Game toolbar above the pane, joins the focus frame, hides the Game tab while active, and keeps mouse-captured games controllable. Requires Godot 4.7+; developed and verified on macOS, other platforms welcome.