How to use PROJECT_VARIABLE_RENAME

In the extremely unlikely event that there is a scripting person on the forums, can anyone tell me how to use PROJECT_VARIABLE_RENAME? What's the syntax? Do I use it with setValue() or something else?

I've read the scripting "guide" in the RH2019 help which is utterly inadequate for my needs. I've tried multiple combinations of of parentheses and curly brackets and with and without value labels and commas - my imagination has now run out of options in this regard. I've looked at every sample script provided with RH2019 and RH2020. I've contact TCS support who have advise they can't help with scripting. 

My next step will be randomly posting on other Adobe forums in the hope that someone there can help...