@Catrope, I would advise to have this switch done asap to avoid people complaining because they are stuck in preview mode and don't want to try to click on something to switch back.

We can show a tooltip that points to the mode switch button. The tooltip will be shown only when the rich text editor is accessed through the link (but not when switching to it in other ways), and will disappear after a few seconds. The tooltip message can be something along the lines of "Switched to visual editing for the preview. Switch back anytime".

I prefer to use a tooltip instead of a separate entry point in this case. A tooltip helps to establish the main switching mechanism as oppose to creating the illusion of a separate preview modes. We provide the "preview" option as a shortcut (it may not be obvious that visual editing can be used as a way to preview), but we want users to learn and use the main switch.

I like your idea, but I'm also lazy: have to click twice to go back to my previous editor is not what I expect as a user.
When I edit a wiki, I clock on "edit" and "edit source" tabs to switch between editors, never on the pen! ;)

In T183382#3892554, @Trizek-WMF wrote:

I like your idea, but I'm also lazy: have to click twice to go back to my previous editor is not what I expect as a user.
When I edit a wiki, I clock on "edit" and "edit source" tabs to switch between editors, never on the pen! ;)

There is a balance we need to find between providing quick access and not crowding the UI. We definitely want to allow advanced editing, but we should be careful not to distract users that just want to provide a quick and simple reply. Similar to what happens with "bold" (which is provided through another menu), we could provide a keyboard shortcut to facilitate the switch for advanced users.

T184701: StructuredDiscussions message editing should support some shortcuts to switch between editors :)