如何在Visual Studio代码launch.json中设置局部变量？

Question

如何在launch.json文件中设置局部变量。即如果我在文件中的某处设置了var myvar = "myvar"，我将如何引用${myvar}？

var myvar = "myvar"
{
    "thing_to_set": "${myvar}" // This does not work
    "version": "0.2.0"
}