However, it's now a little more complicated as sandbox and production accept different params:
The parameter for "?new_existing=Existing_Update" is now "update_creds" (the options are "Yes" and "No").
Find here the complete list of the parameters that can be added to a URL to populate the forms :
Parameter passing has been renabled on API credential requests at the new URLs:
https://info.orcid.org/register-a-client-application-production-member-api/
and
https://info.orcid.org/register-a-client-application-sandbox-member-api/
However, it's now a little more complicated as sandbox and production accept different params:
Would be nice to have this back again.