Glyphs.app's Feature Condition Syntax is not supported

I'm using fontmake to export VF with CFF2 outlines from a Glyphs3 file. It builds the UFO and designspace but then fails when I have this code in the feature rlig:
```
feature rlig {
#ifdef VARIABLE
condition 18 < wght < 278, wdth < 40;
sub dollar by dollar.gap;
sub dollar.ss06 by dollar.ss06.gap;
sub cent by cent.gap;

condition 100 < wght < 278, wdth < 100;
sub dollar by dollar.gap;

condition 152 < wght < 278, wdth < 70;
sub dollar.ss06 by dollar.ss06.gap;
sub cent by cent.gap;

condition 18 < wght < 152, wdth < 40;
sub ampersand by ampersand.comp;

#endif

} rlig;
```

This is the error: `Generating fonts from Designspace failed: :510:1: Expected glyph class definition or statement: got NAME condition`
(line 510 is: condition 18 < wght < 278, wdth < 40;)

Is there way to go around this changing the Glyphs file? Or some other simple solution?