so i don't have to scroll through all the different values i don't need when changing trace width?
also, how do you change the width of the subsequent legs of the trace?
also, is it possible to change the width of a trace, or part of a trace, after it has been laid?
is it possible to use the +/- hotkeys for changing the width of a selected trace?
what's the workflow for changing a trace width in the middle of laying in order to route between pins, for example? do you have to stop/start laying separate traces? or is there a hotkey to start a new trace segment?
Brand new interactions and interfaces. 
Easy to use and quick to get started. 
How to change the width of the whole of a trace.
Highlight the whole of a net.
Edit the trace Width in the Track Properties window.
How to change the width of the segment of a trace.
If the trace was drawn all as one segment then it is not possible to change the length of one part of it without deleting up the part that needs to be changed, by double clicking on either end point.
Then, depending on what segments you have left on the canvas, either set the Routing Width in the Canvas panel to the desired trace width and redraw the missing segment(s) at the new width or select the remaining segment and edit the width to the desired value.
This can be quite time consuming and it is often easier simply to delete the whole track and draw it again but in separate segments each of the desired width.