This menu bar is featured at the bottom right of your screen in any game mode while playing.
The top right button is the undo move button, which sends you back to your previous position after a movement. You can just press Z on your keyboard as a shortcut
The button below is the button to set a checkpoint. You can set a checkpoint at any position during the round, and then click the same button again to return to that position. The shortcut for this is C on your keyboard.
The button on the bottom left will send you back to the spawn location. The shortcut for this is R on your keyboard.
The +/- button on the top right of the menu controls your zoom. The shortcut for this function is the scroll wheel on your mouse/trackpad.
The button below that opens the settings menu of the game.