Just a feedback regarding JS API 4: I find it a pity that you don't support "grouped" values in your legend widget contrary to 3.X.
For example, a layer in MapViewer 3.X:
And in the new MapViewer using 4.X:
We now have to create and maintain a new field solely for visualization purpose: it's a pity !
Thanks for listening !
PS: otherwise it's really cool, and fast, and the developper experience is awesome :)