Contextual Pie-menus, like Radiant menus by Wacom
creating a contextual "shortcut" menu overlapping layer to access quickly Tools. This is a kind of Radiant Menu developed by Wacom on their tablet for example or Alias marking menu. This should really improve workflow ergonomics.
Kimmo Hellstr commented
Illustrator could really use some modern UI design elements, like Pie menus for example.
Some, even basic, features are so frustrating to use as the only way to access them is via buttons in panels. With 4K monitor, this leads to a huge amount of travelling with the mouse.
Like, if you want to change the Width of the stroke, you have to do it from the panel. It should be able to do it, for example by pressing a hotkey, dragging on the screen.
And things like Align “tools” should really be in Pie menus, so you wouldn't need to travel all the way to the top of the screen when you want to align something.
Illustrator is quite frustrating to use, as its UI seems to be stuck in the 2000s or something.
...and there is still no color wheel :(
This could also go in User Interface, but basically if you've ever used Sketch App you know how handy and time-saving contextual tool menus are. When you are using a particular tool, the menus/palettes should update on the fly so that you don't have to continually collapse and expand palettes/menus to access stuff you can do with that tool.