如何在XML配置文件中指定Octopus内置变量名？

We are testing Octopus Deploy, so we made a sample web.config file that we installed and transform in different environments. web.config transformation and use of custom variable work fine, but I can't get build-in Octopus variables to be substituted. Here's an example of of XML section in web.config:We are testing Octopus Deploy, so we made a sam