Hello Marek,
A possible solution is to handle the
DropDownOpened event of RadToolStripItem's DropDownButton. You could access that button by using the
OverFlowManager property of RadToolStripItem which gives you an instance of ToolStripItemsOverFlow class, and then use its
DropDownButton property and subscribe to the
DropDownOpened event of that button.
In the EventHandler you could change the visibility state of the last item, which in our case is the add/remove items menu item, and is a child of the DropDownButton's items collection.
Write back if you need further assistance.
Best wishes,
Ray
the Telerik team