How to use non standard variables from extra field of Zotero?

Question

I have some custom variables that I have created; the variables are stored in the Extra field of Zotero using this format myCustomVariable: myCustumVariableValue\n I would like to access them in the CSL file I have tried to use <text variable="myCustomVariable"/> it seems the correct way from the documentation, but it doesn’t work. Is there any way I can access them and print them in the bibliography generated by Zotero? I could do a custom script in Python, but that would be reinventing CSL…