Documentation about how vars can be defined in foreign bundles in specific circumstances

Documentation about how vars can be defined in foreign bundles in specific circumstances.

how can I overwrite a variable from another bundle?
In version 3.7 it worked, in version 3.15 it, unfortunately, does not work.

  bundle agent main
  {
    vars:
      "my_bundle.my_var" string => "Set from main";
  }
  bundle agent my_bundle
  {
    vars:
     "my_var" string => "Set from my_bundle";
  }