A few UI enhancements for improving the already very good default experience:
- Have the Objects/Type/Styles sections already open at startup (or remember their state across starts)
- Option to separate the Construct/Transform sections: I personally find myself switching between the two frequently and for 27" or larger screens there is enough vertical space to make both directly accessible
- Configure some default keyboard shortcuts for various frequently used tools: This greatly increases the efficiency and it's kind of hard to find out the right commands for configuring those manually

Since the added grouping support in V5 allows to construct more complex designs, it would be nice to have a variation on the orbit mechanics that rotates around the first point of contact below the mouse cursor. Same goes for zoom and pan for scaling the speed/step size. This would allow comfortably working on details in parts of the model that are further from the origin.