To tell AMPL to show a 1-dimensional list of values in one column, set this option before your “display ST;” command:
option display_1col 1000;
When the value of this option (here, 1000) is \geq the number of values to be displayed, then they will appear in one column.
To export the output of “display” to a txt file, add > and the name of the file to the end of the command. For example:
display ST >display.txt;
(If you want to look at the file immediately, you may need to add “close display.txt;” to force the cached file onto your storage device.)