How to pass marginparwidth to includegraphics

[ehud.behar at protonmail.com]

I have some figures which I want to include in the marginal part of the document.
The graphics to be included should be of width \marginparwidth​.
How can I pass this width to the include graphics tool (Insert->Graphics) within the editor?

In plain LaTeX I would have typed

\begin{marginfigure}
\includegraphics[width=\marginparwidth]{file.png}
\end{marginfigure}

(I created a customized marginfigure inset with a module file)

So after inserting the graphics file, I don't see any way to specify the above width.

The only options I have are those in the attached picture, non of which is marginparwidth.
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