App Isolation is a feature layered on top of low level sandbox primitives and IIRC it doesn't support this. On the other hand, it also wouldn't make sense for

App Isolation is a feature layered on top of low level sandbox primitives and IIRC it doesn't support this. On the other hand, it also wouldn't make sense for App Isolation because that's intended to give apps a lightweight way to opt-in to isolating themselves, in order to restrict the blast radius of exploits. It's not intended to let you run arbitrary third party code sandboxed. For that you would need to use something more like the Chromium sandbox that uses kernel job objects, which a sibling comment describes. Using that would require fluency in Win32.