A freshly created structure has two boxes (or nodes) :
If you move the mouse over certain areas near the boxes, small 'hotspot'
images appear to show you where a new box would be added if you were to click
in that place. For example here is the hotspot
that appears to indicate that a new box could be added under the one labelled
'Dummy', and the result of clicking whilst the hotspot was visible:
... and clicking on the hotspot results in ...
Here is an example of a hotspot used to
create a box at the side of another one:
... and clicking on the hotspot results in ...
You can insert a box between a parent and its children using this kind of hotspot:
... and clicking on the hotspot results in ...
To remove a box, right-click on it and choose 'Delete box' from the pop-up
menu that appears:
