Hi res13,
I am not aware of anything for the API Portal side with regards to variables that can be used in place of text for items like GATEWAY_HOST, but it's a great idea, and one that we can definitely review for a future release or timeline. I highly encourage you to submit an idea to our CA API Management community, as ideas are submitted from other customers alike and also by internal employees (including myself) when we feel there is something that can be improved upon or something completely new that we should be doing to make our customers lives easier. Our Product Management team reviews them frequently and will interact with you if they want to ask any more questions as they design it or to perhaps announce that it has been implemented or released. You can create a new idea at the CA API Management community located at ca.com/talkapi and clicking on [Actions] > [Create an idea]. Don't forget to vote on it yourself after it's been filed, as the CA Communities do not auto-vote on your behalf (yet).
Sincerely,
Dustin Dauncey
Support Engineer, Global Customer Success
Email: API-Support@ca.com
Phone: +1 800 225 5224
Outside of North America - ca.com/us/worldwide.aspx
CA API Management Community: ca.com/talkapi