You can sort the order of your pages in the navigation.
After «signing in to the Designer» you will land on the home page of the Designer Editor, which is the area called «Site editor». From here on you will have to proceed as follows:
There is a button with a dropdown icon in the blue bar on the top of the page labeled with the currently showing page in the editor (on screenshot: «Home Page»).
Click on it and the «Pages and folders» area opens.
To sort the links in the navigation move your mouse (cursor) over the «6-dot-icon» of the page or folder you want to move, click, and drag it to the position you want it in. The link will stay in its new position when you release the left mouse button.
Click the «X» icon at the top left when you are happy with the order of the links.
You will have to reload your browser window for the new order to be visible in your navigation (Windows: Ctrl + R / OSX: cmd + R).