I have a 1st floor addition with a sloped roof and vaulted ceiling that extends about a 1/3 of the way up the 2nd floor. To accommodate a pre-existing window on the second floor where the roof intersected the main house, a box sized space was cut into roof and just above vaulted ceiling. The space spanned the width of the window, extended out approx two feet into the roof with a depth approx 2" below the window sill. The space was enclosed in waterproof exterior material and included a drain to prevent water from entering via the window. I'm having difficulty emulating that in Home Designer Pro. I've created a hole in the roof but I've not found a way to create the side walls and bottom of the box shape. I gave the Skyllght function a go hoping to tweak it to remove the ceiling cutout while keeping the sides, but all I ended up with was a hole in the roof and no sides. I've also tried a 3D box with two sides open that I found in the library, but as expected I couldn't find a way to conform the same to match the slope of the roof. Any thoughts on what else I could or what I may be doing wrong? I've attached my basic house plan and a picture of what the roof looks like - you can see the cutout just above the far skylight. As I noted, the top matches the slope of the roof, but the bottom is level. In case the signature doesn't appear I'm running Home Designer Pro 2019 on iMac (High Sierra 10.13.6).
House Plan.plan