Yes, you can! When I did it, though, you had to initially select the same experiences for everyeone, and then you could tinker around and split the FP+. The "nuts and bolts" of the procedure went like this... Say I wanted to schedule a day where all 6 of us did BTMRR and Jungle Cruise, but we split up for Splash Mountain/Aladdin's Magic Carpets:
1 - First, select, reserve and confirm the same 3 FP+ attractions/times for the entire group --in our example, BRMTT, JC and Splash.
2 - Select the FP+ we wish to split (Splash) and click "change experience."
3 - Select the "new" experience for those who don't want to ride Splash (Aladdin's Magic Carpets) and, once the new experience is selected, a drop-down menu will appear showing all party members and bidding you to select those for whom the change will apply. You'd then confirm that the people doing Aladdin's Magic Carpets were selected, and de-select anyone who was keeping the Splash FP+.
4 - If desired, change experience times, as necessary, so that the "split FP+" will be in synch. (We typically split up for attractions that were near one another, so in that case it makes sense to do them at the same time.)
5 - Check and make sure that all FP+ are listed accurately on MDE, including split FP+. (Often, my changes did not display immediately, or only "showed up" if I looked at a single day's itinerary -- the "my reservations" section of MDE would only list 3 FP+ per day, even if there were 4 or 5 for my party due to split FP+. However, they all were accurately recorded in Disney's system, since they all worked perfectly when we went to "use" them.)