It should be able to switch between these three editing possibilities during editing. All of them have their advantages and disadvantages.
Topic on Extension talk:CodeMirror
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This is currently possible, in content pages. See mw:Help:VisualEditor/User_guide#Switching between the visual and wikitext editors for switching between those, and both the 2010 wikitext editor and 2017 wikitext editor contain a codemirror button, the latter within the menu.
Thanks. I expected to select between three options instead two options with one sub-option.