Unfortunately, what you want is currently impossible in design time.
You have two choices:
1. Create the chunk in design time and then hide/collapse it if you do not want it to be visible, and reparent it to another tab if you want it in another tab.
2. Create a method that creates the chunk with all the buttons that you need in it and then use it to create the chunk in run time.
All the best,
the Telerik team