I don't do Partnerships so I'm not the person to ask, but perhaps I can get the ball rolling ...
Can you clarify what you want to "aggregate"? Are you doing the Partnership return or are you doing the 1040? Have you double checked that the 3 year rule of Section 1061 applies to your situation?
As a completely unrelated note, I was surprised when I saw your name "bporter" because MY name is Bill Porter. 😀
About 25 years ago, someone called my office (I was then in public accounting, and a bit younger) and expressed their condolences that Bill Porter had deceased ... of course, the switchboard put them thru to me, as I was not then and am not now deceased !!! .... There was another Bill Porter, a long retired CPA in Atlanta who did decease. Go figure.
So, hello fellow Bill Porter and thank you for your reply.
Bottom line ... I am preparing a partnership return, Form 1065 - that partnership has about 20 investment partnership ownership positions driving partner K-1 inputs ... most of the sub-invest partnerships have capital gains and losses, each of them separating out in the respective input K-1s the differing amounts of LTCG(L) coming from the two categories of holding periods .... and when I get to the end, this Form 1065 will produce K-1s to this partnership's LP's ....
Proseries does not separate out LTCG and LTCL as between the two holding periods, at the K-1 input poitn, so that data has to be added together somewhere so that it can aggregate for reporting on a prorata basis to the ultimate partners ...
I hope it wasn't me that died 25 years ago and I forgot about it. 😂
Ugh, that situation sounds awful. Although I don't know this for sure, I suspect that ProSeries is not set up for the 3 year rule of §1061. If that is the case, you would need to manually calculate everything and override the software. Ick.
Hopefully somebody that deals with Partnerships will come along and either verify that or tell you how to do it. Another POSSIBLE option is that if I remember correctly, ProSeries users can use Lacerte on a Pay-Per-Return basis, and it is more likely that Lacerte would be able to handle it. However, if you never have used Lacerte, that would involve a BIG learning curve, and that would probably be more work than just manually calculating things.