3.3.2 How to organise bill items into a heirarchy of categories

If a bill item is dragged and dropped onto another item, the target becomes a parent category for the dragged item:

Note that the category item displays a folder icon and an adjacent disclosure triangle to expand or collapse the child content. Therefore, categories are created in the same way as bill items – but they become categories at the moment child items are dropped into them. Categories can be nested under categories to any depth, and selections containing any combination of categories and items can be dragged and dropped to rearrange the bill hierarchy.

The only constraint on drag and drop is that items cannot be dragged from one bill to another, e.g. from a bill in an external file the project bill.