These aren’t specific to Cubase 9. They’ve been around for as long as I’ve used Cubase (since v7).
In no particular order:
-Track selection focus when using the track list divider. Like I’m sure most people do, I keep my marker, signature, and tempo tracks in the top portion. I also keep my movie, movie audio, stem printing tracks, etc, plus anything else I need full-time access to while scrolling down through the rest of the project, in the top portion. The problem is: when performing actions where one (or more) tracks from the top portion and one (or more) tracks from the bottom portion are selected at the same time (such as, say, selecting two tracks from both sides of the divider and soloing), said actions don’t behave the same as when it’s performed with two (or more) tracks from the same side of the divider. I always find myself coloring something wrong, or having one tracks solo’d when I don’t mean to, because it just isn’t consistent.
-Related to the last one: tracks in the top portion often end up in strange places in the mix console. Its most consistent behavior seems correct to me: tracks in the top portion should be left-most in the mix console. But for whatever reason, this screws up from time to time.
-Coloring. Can this be simplified, please? Using the track color selector (in the inspector) is fine, but everything beyond that is needlessly complicated. Examples: using the dropdown color menu to color regions often (but not always?) results in a track being colored as well; the “use color for similar selected track” feels like some crummy leftover from the days when Windows XP was the norm–can we just select a few tracks, select a color, and boom, that’s their color now (like how most other DAWs handle this)?
I’m sure there’s more–I’ll add them as they come to mind.