Sandbox is just a tool, that is cheap to use. That soft sandboxing is little effort and when the itch app handles it, it should be easy enough. If you manually set it up, you would have to shift right click the exe and select run as, and enter password and user. I would not use it to test suspected malware. But rather as a precaution, like driving with a seat belt, even when not expecting a car crash. And just like a seat belt, it will not protect against driving from a cliff. It protects against user level attacks, like stealing your session cookie. Those attacks are very nasty, as they circumvent 2fa and password completely (this is not an itch specific problem).
To protect your machine, you should up your scepticim. I made a tips thread about that. In short, do not trust the new and shiny things, even when hosted on itch. Itch has no account verification, so anyone could be an impostor (yes, just like in Among Us, which incidentally is also hosted on itch). But this is general anti-scam advice. Do not trust strangers on the net, the phone, the mail, on a self publishing store... , even if they say they are royality from other countries and have money to give to you.