Hi,
In this case you may add several dummy buttons to the LeftPaneItems collection
of the RibbonApplicationMenu. You should add a RibbonButton, then clear its
LargeImage and Text properties, then set the Enabled property to False for this
button. For example, take a look at the attached sample. There I added three
dummy buttons to make the longest submenu fully visible.
Regards,
-Andrey