You could do this in two steps. First in your text editor, do a search/replace operation where you replace two line endings in a row (ie [LF][LF] or [CR][LF][CR][LF]) with some character that doesn't appear anywhere else in the text. ` for example. Then import the text file as a csv ('comma separated value') file, and change the separator to the character you chose.
(To easily search/replace without needing to know your line ending type, in most text editors you can simply highlight the two lines (from immediately after the 5 in text12345 to the end of the blank line), and copy/paste that into the search box in the search/replace dialog.)
Edit: Here's how to specify a custom delimiter when importing: How do you change default delimiter in the Text Import in Excel?
Also, this question is probably more appropriate to https://superuser.com/ as it's not really programming related.