Tidy overlapped items

The editor will not allow an assembly diagram to be saved if items are overlapped. An error will be displayed:

The overlapped items will be highlighted in red and the editor will attempt to make any hidden items appear on top:

The editor can automatically tidy up any overlapped items by right-clicking on the editor's background and choosing the Tidy menu option:

Alternatively, use the Tidy option from the Edit menu at the top right: