Add resize and evenly space buttons on the Diagram toolbar

[Guillaume]

Hi,

The diagram toolbar can be enabled via the Preferences menu. This is handy when working on diagrams so one doesn't have to open the Layout menu.
The toolbar has some free space that could be filled with the following: evenly space H + V, resize (height, width, both).
Note that I tried to use to Toolbar Customize menu but it doesn't seem to work on the diagram toolbar.