If you want to turn particular storey levels off in all sections/elevations, you can do this in the 'Storey Settings' dialogue.
If you want to turn of all storey markers of in a single section/elevation, you can do that in the 'Section/Elevation Settings' dialogue.
If you want to turn off one particular storey level in one particular section/elevation, I don't think you can do this (except for cover with white lines and fills).
As far as I know storey levels are not something you can control with Graphic Overrides.
Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11