If you do the following, it will allow you to use the ALT+ENTER as delimiter:
Choose Data | Text to Columns
Select Delimited, click Next
Check 'Other', and click in the 'Other' box
Hold the Alt key, and on the number keypad, type: 0010
(you won't see anything in the 'Other' box, but that's
the code for a line break character)
After you let go of the ALT key, you will see how the columns will be split.

"EASY QUESTION" wrote:

It seems that any single character can be used as a delimiter, but no
"ALT-Enter". I come across multiple rows within a single cell ALL the time!
How do I make "ALT-Enter" my delimiter?