I’ve made a custom tool for the editor that lets you scale bezier curves in a similar way to what comes built-in with Glyphs. The idea for these kinds of tools came originally from Interpolated Nudge for FontLab by Christian Robertson of betatype.
The tool inherits all the functionality of the default Editing Tool, adding the curve scaling for mouse and arrow-key movements. It works with open and closed contours, and bicubic and quadratic curves. The offcurve points retain their angles, unless you hit the command-key while having mouse key down. The handles start to expand again below zero point of scale, instead of bending backward as happens with other tools like this. Also, like most similar tools, it can behave unpredictably without points at extremes.
This is the first useful programming I have ever done, so it can be a little wacky, but I am amazed how easy this python thing is to get a handle on. I should keep on improving the tool, if no-one else will.
There are instuctions in Okay Type’s blog by Jackson Cavanaugh on how to add your custom icons for tools in RoboFont. His tedNudget script is another approach to the same idea. You can also easily change the order of the toolbar icons in the latest version of RoboFont.
I’ve just made this into an extension with simple user settings in the contextual menu and a fancy toolbar icon. Enjoy!