How to add context menu on a new message window?

How to add context menu on a new message window?

I’d like to get a selected text on a new message.

I could same on a viewer of receiving mails.

messenger.menus.create({
id: “get_selection_text”,
title: “get_selection_text”
contexts: [“selection”],
onclick: function_treating_text
});

I suggest you ask here:
https://thunderbird.topicbox.com/groups/addons

Thank you for your suggestion.

I’ve made a same thread.