Hi, You might be better off posting here : https://discourse.mozilla.org/c/add-ons Also see : https://developer.mozilla.org/en-US/Add-ons And : https://developer.mozilla.org/en-US/Add-ons#Contact_us

Normally WebExtensions can only access content on web pages and not other Firefox data like preference settings. What you want is information that is from outside Firefox and that would require special techniques to communicate with an external program. There are extensions that can pass information to an external application like download managers and extensions that open pages in another browser, but I don't know if there is a way to pass that information back to the extension. This is really outside the scope of this forum and you will have to check out the Add-ons forum website as posted above (I noticed that the above reply is marked as unhelpful). See also: *https://developer.mozilla.org/Firefox/Multiprocess_Firefox/Message_Manager