Menu problem (cannot add buttons)

First off all: dopus is great an makes my life so much easier.
I found a lot of features in the command list, that I like to add to the toolbar to make it even more useful. Unfortunately I cannot add buttons. I can delete existing ones but can't add any.
I hope someone knows a solution for that.
THank you!

[Drag & Drop does not work for files or when customizing toolbars)