I've made updates to the SAMT messages and done the TPXOPER RELOAD PANEL=TENMSGL command, but the changes have not taken effect.
How to get SAMT and TxxMSGL message changes to take effect?
TPX® Session Management for z/OS
SAMT changes can be implemented without cycling TPX by using TPXOPER:
RELOAD SAMT=tablename
Panel member TxxMSGL contains the one-line messages TPX displays.