This is what I was finding out when playing around; the idea that I need to adjust the heel height to match the structure depth is what was tripping me up.
Yes, which is what brought me to this question, because in X14, this is exactly how it would operate - I could change the pitch as much as I wanted, and it would automatically adjust the "heel height" to compensate, leaving me with my desired structure depth over the exterior wall. At that point, I could raise the roof plane to my desired height, effectively doing exactly what the heel height adjustment from X15 does, but at the end instead of at the front side. The marjority of homes that I work on do not have any sort of raised heel, so if I cannot get X15 to operate as autonomously as X14 did, then I guess I just need to make sure that I adjust my heel height to match structure depth every time I build a roof plane. It just seems messy that you cannot lock the heel height to the structure depth, because now when changing a manual roof plan from say 6 to 8:12, I have to also make sure to change the heel height to match the new structure depth, creating another potential error point. Furthermore, the structure depth is certainly not precise to 1/16", so it is never going to be perfect.
I am in the Pacific Northwest, our energy is pretty stringent. This is more about how the program operates and how/why it changed. It makes intuitive sense to me the way that X14 handled it, and it was more exact. If it was a standard truss, it was perfect out the gate. If I needed an energy heel, I locked the pitch and made the baseline whatever my wall height was +12". Easy.
Ain't that the truth, but at least in this situation it seems like it was, and now it is not. Which I find unfortunate.
I super appreciate you all taking time out to hold my hand and walk me through this stuff. What a great community that has helped me on numerous occasions!