I use these Obervations fields:

dwc:organismID, to relate different observations of a same organism (or a group of them) along the time.

vernacularName, to record the name used (if any) in the place of observation.

Associated observation, because I also post obervations at Natusfera, so we can avoid doubles in case they reach GBIF databases.
Example:
https://www.inaturalist.org/observations/57353966
https://natusfera.gbif.es/observations/72902