Hi @andy570 - I think this would be a great use case for the Range Mask Tool (see attached screenshot): Set the Hue range to 100% to cover the entire hue circle. Limit the Chroma range to be close to the grey axis and give it some feather to only affect neutrals. Then move the Luma range qualifier to wherever mid grey is in your scene and feather the edges as desired. Now when you crank up the "Isolate Grade" slider, your neutrals around mid grey will be left untouched by whatever you do with the look development tools.

I'm planning to add the ability to define multiple ranges so that way you could use the keyer to keep your neutrals clean and use additional qualifications for things like skin etc.