Compressing and expanding part of a toolbar

[don_AC64]

In a toolbar like this:

Item1
Item2
Item3

I would like, by clicking on Item1, to toggle compressing/expanding Item2. So, the first time I click on Item1, the toolbar should appear like this:

>Item1
Item3

The second time I click on Item1, the toolbar should appear like this:

vItem1
Item2
Item3

and so on.