Some of the stuff that have been deprecated for a long time and left in the UI are:
Level Settings Panel - View Distance Low Spec, LDR Global Dens Mult, Waves Speed
Material Editor - Use Scattering, Fur Amount, Clock Amount, Link to Material, Propagate Options, Layer Presets
(I have seen in the Road Map that there should be a new Material Editor, but just thought i would mention them)
Those are just some I have noticed, I pretty sure there is a few more but that is the kind of stuff I am talking about.
One small change I do recommend is for the Environment Editor, Easier to just show rather than explain why the change would be a small improvement.
Now again, I know this is the low priority stuff but some of these small changes would be nice to see sometime soon. Mainly just to help my OCD
