hi richie
I was a bit confused with which Test Step was being used but I had trialed creating a 'JDBC Request' Test Step out on my end with my current SQL JDBC setup and it works as I expect so hopefully the same would work on your end.
So I use the Environments feature of ReadyAPI to change the DB connection configuration of a PostgreSQL DB connection (and prior I had done it for a MS-SQL DB connection) for various Data Source Test steps (which was what I have always used my DB connections within ReadyAPI)
Here is a screenshot of my JDBC connection section in ReadyAPI Environments section
In the gif (ReadyAPI Environment DB Connection.gif) you can see that I have the configuration for 2 separate DB environments and then within the Data Source Test Step using JDBC, when I change the environment it changes the connection but the greyed out section does not change to the new values. My hypothesis is that the greyed out section is from the Default No Environment connection. But this way of configuring allows us to change the config per environment under test (the team using MS-SQL DB has 7 environment configs for their DB connection used in the Data source Test Step)
I also created a dummy JDBC Test Request step and I could see that it was working correctly with the JDBC connection I had created in my project. Although I note that the connection string does change to the string for the environment in the JDBC request, so not sure why the behaviour is different to the Data Source Test Step. (gif attached ReadyAPI JDBC Test Step using Environment.gif)
Try and see if this setup with Environments works for you.
