Compile Harfbuzz with Graphite support enabled.
InDesign 2020 uses Harfbuzz for complex script rendering. Harfbuzz has the capability to use Graphite instructions for rendering complex scripts, but Adobe has compiled Harfbuzz without Graphite support.
Graphite is needed for rendering some character combinations used in languages which are not supported by other font technologies.
Bryant Dresher commented
Agreed, content rendered in a Graphite enabled applications with a Graphite enabled font renders much better and closer to what is natively intended. What would it take to get the Graphite rendering functionality in Harfbuzz enabled in InDesign by Adobe? Is it possible this was just an oversight to include Graphite? We're interested in this for supporting Urdu publishing.
Craig Webb commented
This would aid in correctly rendering Myanmar scripts, too!