The corner window tool should just use the regular windows, but with the corner window tool, I believe that both sides of the corner have to be the same window configuration (maybe not the same width).
It will only show as a regular window in the settings, you will not see the corner configuration.
However you can just use a standard window and turn on the custom corner and then move it to the corner of the walls.
This way you can configure each window differently.
i.e. fixed on one wall and sliding or awning on the other wall.
You will have much better control with separate windows, especially if you want them to be different.
One of the forum moderators. Versions 6.5 to 25 Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10 Dell Precision 3510 - i7 6820HQ @ 2.70GHz, 16GB RAM, AMD FirePro W5130M, Windows 10