As part of our deployment pipeline for z/OS Connect 2.0 provider api's we use the Restful Admin interface in z/OS Connect.

https://www.ibm.com/docs/en/zos-connect/3.0.0?topic=apis-using-restful-administration-interface

We have just started to use z/OS Connect 3.0 in connection with API Requester functionality.

We can't find any information about the Restful Aadministration Interface for z/OS Connect 3.0(openapi 3) ?  Is it not available in the 'new' version of z/OS Connect?

Is there no information about z/OS Connect Restful Admin Interface for z/OS Connect 3.0?

The admin API that where available with OpenAPI2 are not applicable for the way OpenAPI3 artifacts are deployed

OpenAPI3 artifact is a standard J2EE war file, and these are managed in the same way you manage any war file in a Liberty server 

You can use MBeans for example if you wanted to action the war file application

As mentioned there are no REST APIs in OpenAPI3 to do API admin.

See this link which describes how you would manage deployment of OpenAPI3 in a server

https://www.ibm.com/docs/en/zos-connect/3.0.0?topic=30-deploying-apis

That link leads to

https://www.ibm.com/docs/en/zos-connect/3.0.0?topic=building-zos-connect-apis-gradle

and shows that you use

<webApplication location="/config/apps/EmployeesApi.war" name="EmployeesApi" contextRoot="/EmployeesApi"/>