At https://bpy.wikipedia.org while editing a page with the source editor I could use CTRL-M to switch back and forth to writing in Bishnupriya Manipuri.
(Alternatively, there's a checkbox that would allow me to do the same; the same system also works for the edit summary field).
In the visual editor CTRL-M is supposed to do something else entirely and the checkboxes are also missing. (FWIW I only manage to clear styling via CTRL-\ ).