FTM-400 / APRS Text MessagesAPRS Text messages in the Yaesu radios are not saved to permanent memory.
I am referring to those described on page 48 of the APRS manual for the FTM-400 (I would think there are comparable descriptions in the other APRS manuals) . This is a continually changing list of sent and received messages. Once it fills to 100, the oldest messages are deleted automatically to make room for receipt of a new message.
These messages cannot be edited through the programmer since the power off/on sequence needed by that process will clear the list. There are 8 Text Message memories that can be saved. Access them in the program at Settings | Radio Menu Settings | APRS | Text Messges.
APRS Text Messages 08/26/2020