Display Contrast- lost access to controls which had become invisible

I lost ability to alter the contrast which had gone wrong- probably my fault. Could not remedy as all the relevant slide switches had disappeared from the relevant screens for Display in particular. This problem had been reported previously and contributors had suggested doing a safe re-boot. I tried this with total lack of success.

I eventually solved it as follows :-

System Settings

Appearance

Select DARK mode.

Acccessibility

DIsplay

and the toggle switches and sliders were all visible again.

Reset the contrast to normal, returned Appearance from Dark to Light, and all was working fine.