To get the automatic feature generator to work, you need to use certain glyph name suffixes.
Feature
Glyph name
liga - Ligature
Join the glyph names of the components with a "_". The common ligature with "f", "i" and "l" are placed in the liga feature, all other got to dlig.
dlig - Discretionary Ligatures
Join the glyph names of the components with a "_". The common ligature with "f", "i" and "l" are placed in the liga feature, all other got to dlig.
smcp - Small Capitals
Add ".sc" suffix to the glyph name.
sups - Superscript
Add ".sups" or "superior" suffix to the glyph name.
subs - Subscript
Add ".subs" suffix to the glyph name.
sinf - Scientific Inferiors
Add ".sinf" or ".subs" suffix to the glyph name.
dnom - Denominators
Add ".dnom" suffix to the glyph name.
numr - Numerators
Add ".numr" suffix to the glyph name.
onum - Oldstyle Figures
Add ".osf" (for proportional oldstyle figures) or ".tosf" (for tabular oldstyle figures) to the glyph name.
tnum - Tabular Figures
Add ".tf" (for tabular figures) or ".tosf" (for tabular oldstyle figures) to the glyph name.
pnum - Proportional Figures
Add ".osf" (for proportional oldstyle figures) or ".lf" (for proportional lining figures) to the glyph name.
lnum - Lining Figures
Add ".lf" (for proportional lining figures) or ".tf" (for tabular figures) to the glyph name.
hist - Historical Forms
Add ".hist" suffix to the glyph name.
frac - Fractions
The frac feature is generated from a build in list of glyphs.
locl - Localized Forms
The locl feature is generated from a build in list of glyphs.
ssXX - Stylistic Set XX
Add ".ssXX" suffix to the glyph name, for example ".ss01" or ".xx12".