First of all, I'm getting rave reviews from our client about the new 19.6 interface! Well done!
They had a couple of thoughts on the UI, which I'm turning into requests on their behalf. The first request they had is for a "twilight" mode. Right now, there's a dark mode and a light mode, but they're finding the light mode brighter than they'd like, and the dark mode darker than they'd prefer. Also, the window backgrounds are still pure white, even in the dark mode! This makes it not actually all that dark.
They've suggested a color palette similar to the default palette in Power Bi for the modelling mode - cool grays, kinda like this:
I think that would be a nice touch, and be much easier on the eyes than the current options, especially if you're sitting in front of Discovery Hub all day long.