Now the behaviour of the Navigator-View is as follows:
Double-clicking jumps to the corresponding place in the
file. And Right-Clicking brings up a context menu,
where it is possible to insert references to that item.
It would be easier for the user, if he/she could insert
a reference just by Ctrl + Double-Clicking on it.
Shift + Double-Clicking shall insert a pageref.
And Ctrl + Shift + Double-Clicking the label itself.