Yes. You can specify your favorite macros and add your favorite packages (this is a list of LaTeX packages we support)

Macros and packages are defined in a file called header.tex, which you can access by clicking on the Edit Macros in the toolbar, under Settings ⚙

Macros

\newcommand{\msun}{\,\mathrm{M}_\odot}
and then go back to your article and write in a LaTeX block Hello $\msun$, you will generate “Hello M⊙”.

Packages