In the interface, your categories are displayed as they are on your online shop (front office).
You can quickly and in a very simple way re-arrange their order by a simple drag/drop.
Indeed, you just need to select a category to drag and drop it wherever you need it to be.
On the first screenshot, you can move a category between two, and on the second screenshot, you can place a category within another one (making it a sub-category).
The change is applied in real time on your front office. No need to save or synchronize anything!