There is a new version of VTT, (6.20), available for download. VTT now allows for the easy addition of hinting to Variable Fonts. Download VisualTrueType 6.20.
@Georg Seifert : Support for variation fonts is in the current freetype dev code and apparently a new release (2.7.2 or 2.8.0) will be out soon, hopefully in a matter of days.
Georg, any DWrite or GDI app (modulo some obscure rendering modes an app might choose) should support this style of hinting when running on Windows 10 Creators Update.
Comments
https://github.com/unicode-org/text-rendering-tests/tree/master/fonts
Try it out in the new VTT, version 6.2