Yes, this is achievable, but remember if you simply used the Color Similarity Mask again on the same color you’d get the same area masked off.
So in effect you need to use something different, like the Brush Mask to select portions of the Color Similarity Mask you’ve already created that you now want to erase…
Here’s one way:
After creating the Color Similarity Mask you mentioned, keep it on to make it visible.
Then next go to Brush mask (turn it on) and check “Eraser Mode.” Then Click on the icon to “Add the brush mask on top of the other masks.” Then select the brush icon to begin erasing the portion of your Color Similarity Mask that you no longer want to be masked. Your brushing will likely be a different color (orange?) than the original mask (yellow?).
Once you let go of the brush, the portion of the original (yellow) mask will be erased.
As with other masks, you can adjust the feathering, opacity, etc.
Once you’re happy with the newly-edited combined mask (presumably masking less of the Color Similarity Mask as you intended), then go ahead and make whatever ART-edit adjustments in the Local Editing tab you were hoping to achieve in the first place - now applied to a subset of the Color Similarity Mask area than originally captured.
HTH.
There are likely other ways (inverted masks, intersection features, etc.) to accomplish this. But it would seem that a brush mask in eraser mode would be to me the most intuitive way to remove some portion of a color similarity mask that captured too much of your image than you intended.