dunno if it'll speed things along a bit but aseprite will create a palette from an image you load and then let you save it out to png or whatever. iirc photoshop can do this too. (example attached) i imagine you could use that to filter out the final result as well
Well when bringing in a reference image you could for instance create little dabs where you want to extract the colors from. Overall what I am trying to get at is that going for a "real" palette directly can prevent this kind of flexibility. But that said it seems to clearly work well for you, so my point is moot really :D…