We’ve open-sourced our custom user interface that allows our users to easily add or update specific iNaturalist observation fields. It’s clunky to do this on iNaturalist’s web interface, and the Android and iOS interfaces only support adding observation fields (as part of projects) to your own observations.
Our solution is hosted as a (serverless) Static Web App on Microsoft Azure with a Function App for making authenticated API requests, so is very cheap to run.
The user is authenticated using the Authorization Code Flow prior to updating the observation fields.
We’re hoping others will be able to adapt this project to meet their needs.
See https://github.com/EcoNet-NZ/inaturalist-weed-status-updater for further details.