The method off accessing the balloon data when adding a balloon to a stack for a hidden part or a part with no geometry is ludicrous (unless thereis a better way I didnt find yet).
so you have a bolt, for example with a balloon on it.
you add to stack
you have another empty balloon that wants to have a washer, or some loctite or something referenced in it.
Now you have to click the left hand tab in the feature manager, find a view with the part in it, dive into the reference tree of that view, find the part, and even then you are not done, you have to drill down into that part, find the origin within that part and click on that!
Now the right balloon number appears in the balloon.
But, yes there right in front of you is the BOM with that desired balloon number in it. It should be possible to copy special or something that number and add it to stack directly. That is how it was done in the cad system i used 20 or more years ago. In fact any text string could be copied from the BOM and placed in any note, and remain linked to the part data.
Isn't progress a wonderful thing.