In reply to Contextual kerning (LookupType 8, chaining contextual positioning):
"FontLab Studio currently does not support:
GSUB lookup type 2 (Multiple substitution, e.g. a b -> c d)
GPOS lookup types 3 (Cursive attachment positioning), 4 (Mark-to-Base attachment positioning), 5 (Mark-to-Ligature attachment
positioning), 6 (Mark-to-Mark attachment positioning), 7
(Contextual positioning), 8 (Chaining contextual positioning)"
Manual, p. 835
So VOLT or FontForge...
