"Curve EQ" is an extension that lets you quickly balance the Bézier handles of a curve, or change its curvature interactively.
Select the curve adjustment method from the window and click "Equalize selected" to apply the adjustment to the current selection in the glyph window.
Curve Equalizer for Glyphs
Curve Equalizer for Glyphs is included in this repository, but it is not working yet. Currently I have no time to develop it further. You are welcome to have a look at what’s there and send pull requests ;)