The code I provided (and most TS code that exists) works in EAs.

There are 2 ways to see the TS works - Red SL line on a chart, corresponding to TS level will be moving once your trade made profit of TS value and the Terminal 'S/L' value will be changing as well. EA will show a 'smiling face' icon in the right top corner of the chart.

There are many variations and options of TS code.

In general, scripts are meant to be used for a one-off execution, while TS needs to be reviewed on every tick.
I find the method explained by newdigital above awkward to use, but that is MQ4 limitation.