Ordering in categories is slightly different to reordering in folders in that you can order both pinned folders and pages in the category. 

To reorder a page &/or folder, first ensure the page is "pinned" (click on the context dot menu next to item and click "pin"). Once the page or folders are pinned, you will see a drag handle (9 dots) appear next to the item in the list, click and drag the page/folder into the desired order. 

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