Hello, For 2 unsuccessful hours of trials, Mistral didn't help me, nor the configuration editor (but there are so many parameters...). On Windows 10, with Thunderbird 140.7.2esr : when clicking on http/https links in messages, I would like to make thunderbird opening my web browser but in private mode, while this mode is not the default one. I know the flag to use to run the browser in private mode from a command line, and it works. But i do not know how to declare it for/in Thunderbird. Mistral answered me that there is a network.protocol-handler.http param to set, but i have not found it or somewhat similar in the config editor. Any help would be welcome. Even better would be to be able to choose through a contextual menu how to open the link, as it is possible in the web browser. Thank for any hint.