Collections can be moved within their collection tree. To move a collection simply press on the actions button to the right of the collection's name and select 'Move this category'.

On pressing this the move collection interface will appear at the bottom of the collection manager, showing the collection's current location. To move the collection press on the edit button next to the this location.

Use the select boxes to navigate through the tree and find the new location for the collection and press 'OK'.