2020 and seemingly still no solution for this minor problem. It’s just a simple question of recognizing the Devanagari ligitures.
Instead of displaying correctly (Platform: mac OS; Application: Simply every app ever on mac OS, here TextEdit; Font: Google-Fonts Baloo 2; syllable to be displayed: "kscham"):
it shows(Affinity Designer 1.8.1, late March 2020):
The problem could be identified as a false handling of Open Type implemented ligatures resp. of false interpretation or omitting of the so called zero width joiner (Unicode codepoint U+200D).
Dear Affinity Team, could you please please fix that issue after three years of users asking. Thanks a lot for your efforts in advance!