Bug: Options lost when switching between visual editor and markdown script

Hello everyone,

I have encountered a problem where switching between the markdown source code and the visual editor changes the options/script which leads to non-reproducible behavior.

Specifically, these lines are not kept after switching to visual editor:

\begin{landscape}
``(plus a third tic which I cannot enter here because this board uses the same syntax)
\end{landscape}
``(plus a third tic)

I use these lines in order to have one (and one only) page in landscape mode. In between these two lines there is a plot embedded. Switching to markdown removes the {=tex} and the .