OVH Public Cloud - Adding region to exisiting vRack
This can be done using the OVHCloud API. It's very straightforward, you can use the web based API explorer to make API calls, so it can all be done within the browser.
The endpoint you are interested in is https://api.ovh.com/console/#/cloud/project/%7BserviceName%7D/network/private/%7BnetworkId%7D/region#POST.
To get serviceName, which is your project ID and networkId you can use the API as well.