It’s definitely possible with both Apache and NGINX for web stuff, you can add to the configs just as you might for a standalone install. Are you asking for a GUI way to do it within Virtualmin? If so, check the Virtualmin > Services > Configure Website (or Configure SSL Website) section, then the Proxying page. Some nice GUI-assisted features may be restricted to Pro.
However for more control you can always just hack the configs directly; if so use the Edit Directives page (remember to apply your changes using the reload button in top-right corner on the Configure page).
Cue the usual warnings about taking care over the scope of any reverse proxy and considering which clients you actually wish to serve, etc.
Some starter references include:
I’m sure us lot here can suggest some good example code snippets if you’re not sure how to configure a reverse proxy manually through the Virtualmin web pages. There’s also quite a few useful examples to get you started on serverfault and superuser if you want to DIY something.