What are you exactly doing? When I export to Excel all contacts I get notes as long as I want. Another issue may be that the CR and LF characters in notes will appear as a little square when clicking in the field or as a vertical bar when looking inthe formula bar.
You may have to add a column with e.g. in cell CO2 =CLEAN(CA2)
[When I look at the imported file the notes are in column CO and CN is the last used.]
You could even start in cell CO1
Propagate the formula by double clicking on the fill handle. As probably not all cells in column CN will be filled you may have o check and fill in different manner. That is probably no problem.
[THE CRLF (and TAB) will disappear; however, no spaces will be added]
Copy the column and paste value at the same place. Now you could delete column CA or directly paste values of CO in CA.
Maybe this is what you re looking for. Else clarify.
NOTE If you want to replace the ?non printable? characters, use three nested SUBSTITUTE with old text CHAR(13), CHAR(10) and CHAR(9) for CR LF and TAB and a space as new character.
If needed apply TRIM on the result to remove superfluous spaces.
=trim(substitute(substitute(substitute(CA2;char(13);? ?);char(10);? ?);char(9);? ?))
NOTE It may be necessary to replace the list separator ; [semi colon] by , [comma], this depending on your regional settings.
Good luck.