I have a boot camp partition on my SSD in my nMP, on which I am running Windows 10 Pro - this has been working for ages. However, since the upgrade to Catalina I have experience one big problem with this setup:
If I use boot manager to get into Windows, when I reboot from inside Windows, the shutdown procedure stalls. I eventually have to stop/start, and the system now defaults to WIndows. I get the sense that the problem is that Windows is not able to update the boot files correctly - which is why it hangs, and why it defaults to WIndows.