Today I was surprised to see that the 3D Document Settings Dialog's Model Display panel contains a Hidden Edges checkbox. If you check it it will display all edges hidden by geometry.
I was not even aware we had such a feature. And it was there even in AC17!
Loving Archicad since 1995 - Find Archicad Tips at x.com/laszlonagy
AMD Ryzen9 5900X CPU, 64 GB RAM 3600 MHz, Nvidia GTX 1060 6GB, 500 GB NVMe SSD
2x28" (2560x1440), Windows 10 PRO ENG, Ac20-Ac28