If you "Fill Uncut Surfaces with: Own Surface colours (Shaded)", you will find you don't have the shadow fill and colour option.
Choose "Non-Shaded" and you can control the shadows.
Barry.
One of the forum moderators.
Versions 6.5 to 27
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11