Layer7 API Management

Where is the API Proxy URL host configured/defined?  We have multiple gateway clusters, how is it determined which particular cluster ends up being the Proxy URL host displayed in the developer portal Proxy URL as shown below:

This cannot be configured/changed. The API Proxy URL is a placeholder for the GUI and not necessarily what is used as the proxy. 
When multiple proxies are used the API should be deployed to all of them. 

If this is testing with API Explorer and you need to use an alternate proxy it can be set in the basic settings of the portal.

This is unfortunately confusing to our API developers, especially because the current Proxy URL host value is incorrect, and doesn't represent any of our CA Gateway clusters.