... if there happens to be a short-cut key combination that allows me to trigger a script that minimises all existing Explorer windows (background and/or foreground) ...
There is a shortcut key combination for minimising windows, but I'm not sure it works for this issue. You can use WIN+D to minimise everything and return to the desktop.
There have been a few new posts recently, so I just wanted to remind any newcomers that we believe we understand when this issue happens - it is not random and seems to be related to group policy updates. It can be reproduced manually by running gpupdate /force from a command prompt (assuming there is an explorer window in the background that hasn't already been affected by the issue or manually minimised). Group policy updates occur on all versions of Windows 11, even Home and PCs not connected to an active directory. In theory, the issue could be solved by Home users, but that doesn't help all us poor sods trying to get work done.
Lastly, we believe Microsoft has fixed this in a developer edition of Windows, and there is hope that an update will be released to fix it soon. EDIT: But a fix is already frustratingly LATE.