Behind the scenes of the LIST Data task is PROC PRINT. If you create a TXT file (Listing Destination output), using LIST Data task (PROC PRINT), then you cannot wrap text. If you create a TXT file (Listing Destination output), using PROC REPORT code, then you can wrap text.
If you switch over to the world of ODS (and use ODS RTF, ODS PDF or ODS HTML), you CAN wrap text for those destinations' output files by using the CELLWIDTH style attribute. The CELLWIDTH technique will even work for PROC PRINT -- but ONLY with those 3 destinations (NOT LISTING Destination, therefore, not TXT).
The bottom line is that if you are using the List Data task and sending your output to the LISTING destination (TXT file), then there is no way to force wrapping. You can use the FLOW and WIDTH options with PROC REPORT -- but this only works for LISTING.
Perhaps this table will convey the information better. PRINT and List Data Task are the same thing in this table. LISTING destination and TXT file are the same thing:
PROC DESTINATION TECHNIQUE WORK
---------------- ---------------- ------------- ----
PRINT/LIST Data Listing(TXT) change format NO
REPORT Listing(TXT) FLOW/WIDTH YES
REPORT ODS destination FLOW/WIDTH NO
REPORT/PRINT ODS HTML CELLWIDTH YES
REPORT/PRINT ODS RTF CELLWIDTH YES
REPORT/PRINT ODS PDF CELLWIDTH YES
REPORT/PRINT Listing(TXT) CELLWIDTH NO