Ability to force the selection of the markdown editor

[Warning39]

I made the following comments in an issue - #3762 (comment) that I logged earlier.

There is a bit of extra friction with that limitation. I've noticed that the markdown editor in marimo only works with r strings and not f or rf strings. Is there a reason for that limitation?

So instead of being able to type this into the markdown editor:

### Some Heading

<img src="public/SolarEnergyDistribution.png" width="600"/>

Some formula $F = ma$ 

I have to edit via the code editor as opposed to the markdown editor, i.e.

mo.md(rf"""
### Some Heading

{mo.image("public/SolarEnergyDistribution.png", width=600)}

Some formula $F = ma$
""")

@mscolnick replied with:

Regarding the mo.md() string formatted, there we edge cases such as lack of auto-completion of the python code when parameterizing the markdown editor. We can maybe revisit this to add support for this, but for now this needs to happen in Python.

How about an option to override this in the GUI on a per-cell basis. If I have a cell with a lot of markdown and just need the odd bit of python code in it like the example above to call mo.image() then I'd be happy in this case to miss out python auto-completion in this cell.