2 iCloud accounts on one computer?

I would think so as well. Adding an iCloud email in Outlook is very easy but I have looked and looked and tried various things and no joy for Contacts and Calendars! I even opened both accounts in separate Windows using Edge thinking perhaps I could drag contents of one to the other and that appears not to work either. I haven't tried the same thing with Safari. Perhaps that will work.

Well, I can't see any reason why a single user would have more than one iCloud account - there would be no benefit to it - so I assumed he was referring to multiple users on one computer...

Not in one user account.

Yes, one will be the primary and the other will the secondary.

How to do it would be nice addition to your answer.

Enter the first conventionally, enter the second in Internet Accounts.

Exactly the same advice as was given in Roger Wilmuts previous post.

I have never and would never use Windows, so no idea.

Control panel has Internet Options but I haven't found Internet Accounts.

The iCloud for Windows applet does not offer this feature.

The tip offered was for macOS only.

I may not know how but I am sure that Windows allows more than one account at a time to be connected.