In my Add-on SmartTemplates I am adding a menu button to the header-view-toolbox, which replaces (template selection) menus I used to add tot he reply / forward buttons.

I was asked by a user whether the button could be removed (they only use the account specific templates that are triggered automatically when opening Composer or selecting a different identity in composer window) and had to admit that it wasn't possible. The particular profile was configured to show the buttons as "text only" and my button title "follow up with smarttemplates" took up quite a bit of space.

Can we provide an API to remove or better move the button to the overflow / more menu? Could the label be hidden automatically if there is not enough space or the UI gets cramped?

We need to put this decision in the users hands, without deviating the API from the Firefox implementation. Currently, add-on buttons in the message header pane are not customizable.

I would like to propose the following:

• Add a context menu entry to all message_display_action buttons, allowing them to be hidden
• Add an "Add-on" menu entry to the "more" menu, where all add-on buttons have a checkbox menu entry and the user can hide/unhide add-on buttons

@Alessandro: Does that sound feasible?

This is probably related to bug 1773314.
I always wanted to implement the ability to hide/show buttons in the message area somewhere inside the more > customize..., but never had the time to fully explore it.
It needs some good UX design, let's sync up on it next week and come up with an action plan.