As I said, only when the code specifies what it should be replaced with will it provide that. You can see all options when you edit the text. For example, in this text, you have lots of options. But that’s rare.
Most texts do not offer more variables than they use. If the text you want to customize doesn’t offer any, then you can’t use them. Also, usually you cannot use markdown syntax in texts. Instead, HTML is used. But that only works when it’s allowed for that text.