To add a linked balloon to the note, just edit the note text, and click on the appropriate balloon in a drawing view. If the view is on another sheet, you can use Window…New Window to create a second window of the same drawing and show the appropriate sheet so that you can click the balloon.
JSculley has answered your question. The only thing I’ll add is that you can add the number without the “balloon” by creating a dummy instance of the balloon, modify it to remove the balloon surrounding the number. Then you can add it to the text box. Then you can delete the balloon.
(Click to see animation)
Which can be especially dangerous if you use the ‘Follow assembly order’ option for your BOMs. Rearranging the items in the feature tree will not be reflected in the linked notes. That’s why I don’t delete the balloon, but place it outside the sheet border.
If you right click the note and select ‘Edit text in window’ you will see that the text for the linked balloon is tied to a particular object id which is the object ID of the balloon itself. The object IDs change when balloons are moved from one item to another or the underlying components are rearranged. If you delete the balloon, the note will still be pointing to the object id of the deleted balloon, which will never change.
That makes sense. I remember looking into it and remember something like this. It’s why getting item numbers in view titles is so cumbersome. There’s no good way to link back to the BOM.