Thank you for your response. I just want to check,k are you referring to Word 2016? I have always used the Home key and the Undo command exactly as you describe in Word 2010. Since Microsoft has made it almost impossible to obtain Word 2010, I bought a Word 365 subscription.

I started Word in safe mode, as you suggested, and holding down the CTRL key while depressing Home still does nothing. Neither does CTRL+End.

This time when I opened the program, it asked me to sign in to Microsoft. Is that going to be necessary every time I wish to work in Word 365?

The Undo arrow did appear in the Quick Access Tool Bar this time.

I work as an editor, and not having a Home/End function and having to sign in every time I wish to use Word will be a real problem for me.