Master Mount

Ground, flying, and swim buttons, with an optional mount after you stand still. Each button can be turned off, which also turns off that button's auto cast. Drag a mount onto a button to assign it.

Forever has ground mounts only, so the flying and swim buttons are not shown there.

The bar accounts for the pet bar and the stance bar. It hides while you are on a flight path or in a vehicle. If combat starts before the bar can move out from behind the pet bar, it fades until combat ends.

Options

Esc, then Options, then AddOns, then Master Mount.