I would start with reading through the NIPs. Then see if there is a code library that has implemeted a note kind that suits your needs.

I don't know what langauge is needed to build plugins for Obsidian, thats the language i would look for a nostr library for. — This is a comment on: https://yakihonne.com/flash-news/nevent1qqp52ajnqgsx8zd7vjg70d5na8ek3m8g3lx3ghc8cp5d9sdm4epy0wd4aape6vsrqsqqqqqp9dt0t3