You must have the write privileges for the SLOs feature in the Observability section of the Kibana feature privileges.
POST /s/{spaceId}/api/observability/slos/{sloId}/disable
curl \ --request POST 'https://<KIBANA_URL>/s/default/api/observability/slos/9c235211-6834-11ea-a78c-6feb38a34414/disable' \ --header "Authorization: $API_KEY" \ --header "kbn-xsrf: string"