The Problem: Multiple OS's (Mac OS, Windows 10 VM for instance) both use a lot of memory. Windows 10 is resource hungry anyway (Defender is a resource hog, ssp, telemetry, etc...). Add to that Chrome browser memory and CPU hits, and sometimes things slow down .. ESPECIALLY Switching between apps or active windows - including between the Mac OS and the VM. A useful Toolbox utility (if it could be kept from making the problem noticeably worse) would be to monitor USAGE of RESOURCES - as they BEGIN to approach EXHAUSTING RESOURCES enough to hamper productivity, to DETECT what needs to change, and ALERT the user. Sometimes it is not Windows at all. It is Parallels itself that needs to be restarted, or the Mac OS platform altogether. Sometimes it is Windows. SOLUTION: AUTO detecting and alerting would help, since when Windows reaches a certain point, even launching Resource Monitor or Task Manager can take forever. It's too late by then. And sometimes it turns out that it is PARALLELS itself that needed to be restarted.