I have reported the details below to support but add here for the benefit of anyone else who may be having problems.
I have isolated the cause of the issue. As mentioned previously, using Parallels eventually causes my iMac 2019 to become catastrophically unstable leaving me no option but to hard re-boot. Whatever is happening causes the UI to become unresponsive leading to a spinning beach ball on any app I try to interact with that requires any UI refresh. The network connection is no longer working: I was hoping to SSH into the iMac from my laptop to run the trouble reporter remotely but the iMac is not reachable over the network - I can't even ping it (I can ping other devices on the network, including the router) Parallels Desktop will not even Force Quit via Activity Monitor.
This issue occurs when the Arduino Create Plugin is active and Parallels Desktop is running. WhenParallels is not running I have no problem with stability at all, and no issue with programming any connected Arduino. It's worth mentioning that I don't have an Arduino connected at the time of these problems, the Arduino Create plugin is running in the background.
If I pause the Arduino Create plugin, then I experience no problems with Parallels Desktop.
For troubleshooting purposes, the Arduino Create plugin can be found here:
https://create.arduino.cc/getting-started/plugin It's a free download. Obviously, I don't know what is misbehaving, but as I say, I only have the issue when Parallels Desktop is running at the same time as the plugin.
This has happened consistently every single time. It has happened on my 2019 iMac and my old 2012 iMac. It is consistent across V14 and V15 of Parallels.
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