To move a menu option within the same tree simply drag & drop it into the new location.
By clicking and starting to drag a blue dashed border will be shown where the menu option will be placed once you release the mouse button.
Create sub menus in the same way by moving the menu option your dragging further left. A minus ( - ) icon will appear against the menu your about to set as the parent for the options you are moving.
Removing a menu option from the tree drag it to the left list of options.
Adding a menu option to a tree drag it from the left list of options to the menu tree on the right