Rather than using the pet palette edge angle option to join the roof edges in a multi-pitch scenario like yours (which is really the same as a shed dormer), use the "Intersect Roof Planes" feature. (The pet palette works for ridges - plumb cut - and other times when you know the angle for a clean joint. With a shed dormer, or pitch change as in your case, a clean intersection requires a peculiar angle. Let ArchiCAD do the math.)
Pull the upper roof edge upwards and the lower roof edge downwards to make them easiest to see and deal with while learning this.
Select the upper roof and then ctrl-click (cmd-click Mac)on the top edge of the lower roof.
Then select the lower roof (only) and ctrl-click (cmd-click Mac) on the lower edge of the upper roof.
Both roofs will meet in a clean intersection when viewed in 3D or section.
I usually prefer to do this in 3D, but same steps in 2D or 3D.
Karl
PS This is basic training - I do hope you sign up for the free 'Jump Start' class.
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AC 28 USA and earlier • macOS Sonoma 14.7.1, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB