There appear to be no diacritics on the romanisation version of many of the consonants that need them. Obviously this makes it difficult to recognize the difference between, for example, ට (ṭa) and ත (ta), ඪ (ḍha) and ධ (dha) or ණ (ṇa) and න (na) in transliteration.
Can this be fixed or do I have to create a whole new course myself just to correct these shortcomings?
It looks like the course’s creator, cactus9, isn’t on the forums.
The current procedure for this is basically to tag @Lien and ask if she can contact the course’s creator and invite them to the forums for them to look at your thread. If they don’t respond in awhile, then you can ask to be added as a contributor to the course, where you’d be able to make the changes yourself if you wanted.