Hi Johan,
You can review the current DAM APIs available directly on your DAM API service:
https://<hostname>>/dx/api/dam/v1/explorer/
For the Collections API, we do not have a way to set access on a Collection with our current APIs (CF191). Please submit a feature request for this functionality here:
https://www.hcltechsw.com/resources/submit-idea
Thank you,
Oscar