In VB or .NET, such a thing doesn't exist. But why not implement it and make it as such it is homogeneous with the rest of the PropertyGrid? Well, it now exists and it has been proved flawlessly with the addition of radio buttons. It integrates correctly in the layout and in the navigation of the tree.
In a few words, this feature allows you to create a property whose height is a multiple of the basic row height. Of course I plan to also add new property feels that will take advantage of this feature, amongst others a group of checkboxes and a multiline edit control.