I think it was with ArcPro version 3.4 when a rather nifty capability was added to vector layer unique symbology; you can now tick on/off the display of the individual symbol by ticking on/off the checkbox. I highlight below.

I find this functionality very useful when exploring data, dropping the visibility of specific features immediately, without the need of writing a definition query.
My idea is that this functionality is to be made available for raster layers displaying unique values.
This would be particularly useful when viewing land cover maps, I simply want to drop from display "Urban" or "Woodland" whilst exploring the results of some geoprocessing.