You can't, because UDrop Pro 'assumes' that you have already built your models with your favorite application.
Custom properties can't help you?
I cannot imagine what you need but knowing the names of the bones/childs of a mesh you can set custom properties (for this mesh) setting the Name of the bone/child and the Value you want.
Custom properties can't help you?
I cannot imagine what you need but knowing the names of the bones/childs of a mesh you can set custom properties (for this mesh) setting the Name of the bone/child and the Value you want.