For some reason, I can’t make SuperTool work in version 3.0. It shows up in the menu bar as expected, but nothing happens when I turn on Show Curvature. In version 2.6.5 it works without any issues.
I have the same issue, except that when I try to select nodes with Supertool on, Glyphs 3 crashes.
I believe that SuperTool needs to be updated to work with Glyphs 3.