Are you asking for the ability to add balloons to your Assembly Drawing which contains the same Callout letter/number that you would have gotten IF you had actually generated a Parts List note? If that is what you're asking for, the answer is NO (this might be different if Teamcenter is in the picture as it has it's own concept of a Parts List and it might be able to impose that on an Assembly Drawing with or without an actual Parts List note).
The reason that I say NO (but with the Teamcenter caveat in mind) is that it's the act of CREATING the Parts List note that assigns the Callout letters/numbers to the Components of the Drawing Assembly in the first place. Until the Parts List note is generated,
there are NO Callouts assigned. And even if you were to manually create the Callout Attributes, that would not help since the only mechanism available to force a manually placed Balloon to update in such a manner that it reflects the letter/number entered as the Callout attribute is to force an update of the Parts List note itself. Without the note, there's nothing to select and ask that it update.
Now if your only concern if NOT seeing the Parts List note on your drawing but you still want the balloons to be displayed AS IF there was a Parts List note is to create the note, update the balloons and then simply hide the note.
Now what
Cowski alluded to is possible, but for it be easy to apply and update, you're going to need to write some sort of custom application and depending on how much automation you want, it could get very complicated.
John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Digital Factory
Cypress, CA
Siemens PLM:
UG/NX Museum:
To an Engineer, the glass is twice as big as it needs to be.