I would try this:
Use PM on the balloon to set the item number. It will link with the BOM item No.
After the few balloons are completed, sort the BOM on item No.
The low numbers with balloons will be grouped.
Group select the unwanted high number lines, set them to hidden.
Your license maybe expired and you may not be able to place an ER, but you can put this in as an
Idea. (upper right corner)
What you can do with your BOM is drag the items in the order you want them in providing they don't break
parent/child relationships. I would leave your balloons linked to the item number and you can RC on any BOM
line item and hide them.
If I am not wrong about you 2nd wish, than this will may fulfill your wish I hpoe
"Right mouse button select the item in the feature manager and select component properties. in the dialogue box there is a check box in the RH bottom corner "Exclude from Bill of Materials". this will remove the part from the BOM".
normally items in BOM get sorted as they are in part tree. But like I said, I'd exclude all parts from BOM that don't have baloons attached to them.
Be aware of the sort by assembly order button. Light color = not active.
It will prevent sorting as someone may want to do according to a desired balloon sequence!