Bootcamp partitioning stuck on 'Status: Idle'

Solution 1:

Resizing the container where Catalina is installed can take an extremely long time. In fact, if you issue a diskutil apfs resizeContainer command, you can get a message stating this. Also, the message will state resizing can execute faster if you boot to macOS Recovery. The Boot Camp Assistant must use the same software to resize and make space for Windows, but no warning is issued with respect to time. So, I can see where a user would conclude something is wrong, when in fact it really does take that long to resize.

Restarting the Mac, during resizing of the container where Catalina is install, probably would cause the container to be corrupted. You could try boot to macOS Recovery over the internet and then use the Disk Utility to run Fist Aid on the container.