How does this work?
I just installed nlopt and the plugin, but I'm unable to find it anywhere..... It doesn't show up in the menus, I can't find any icon.. etc
Basically.. it's installed. Now what?

Please add a license; I suggest GPL v3 to make it compatible with other spacing plugins :)

Allow the NSView to get focus. Support use of key left and key right to nudge the spacing.

Keep a list of what the user has set, rather than just modifying the current status. This will avoid a lot of the "bounce" issues.

Is it possible to include the nlopt library in the plugin?

We're currently using COBYLA, but another of the algorithms from http://ab-initio.mit.edu/wiki/index.php/NLopt_Algorithms might give better results. Should also try adjusting the tolerance, because currently it's a lot happier to bust the constraints than it should be.

Per https://forum.glyphsapp.com/t/converting-to-linked-sidebearings/4870 I wonder if this can be used to 'compact' or 'expand' a set of 'static' sidebearings to 'linked'?