I am planning concurrent fast pass times for some attractions so our group can split up. Is there anyway to build this into the touring plan?
Unfortunately the TP engine assumes that you will be doing all the attractions on the plan. The work-around would be to set up an appropriately sized break to account for the time you will be splitting up and doing the attractions. Your best bet would be to make it a Meal break at a restaurant close to the attractions in question so that the TP engine knows where in general you will be and it can account for walk distances/times when planning everything else.
We have a few times when our party is splitting up and I handled it a couple ways. When we are all in the same area and waits will not be too bad (like one group has FPP for Pooh and one has them for 7DMT and then we meet back up) I just put them in back to back and figured the extra few minutes will get used up finding each other again or going to the bathroom or something.
For some things I just made a note about what the other party will be doing (like visiting the Boneyard while older siblings do other Dinoland stuff).
One of our days, I made two different TPs, optimized one (the one with more rides that might have longer waits) and got it how I wanted, then moved things around on the other plan so that the things we are doing together lined up.
I haven’t tested my plans yet so take my advice with a grain of salt but that’s how I have been doing it.