This is not a SQL Assistant problem. I have the same problem and it is the ODBC driver which is at fault. If you connect via .NET rather than ODBC the query will work. I saw this problem with SQLA 220.127.116.11 and ODBC 18.104.22.168.
I have raised an incident and received this from TD Support: "The problem you are seeing with SQLAssistant 13.0 not showing all the lines of SHOW command in answer/output window is actually an ODBC problem, which is documented in knowledge article KAP1B2D52. The workaround for TTU 13.0 is to downgrade the ODBC driver to 22.214.171.124 or use .Net. The fix for TTU 13.10 is included in 13.10.00.03."