To add a new line to the default text area in messageML, textarea, use the HTML entity to insert a new line.
For example, the code in Figure 1 will be displayed as shown in Figure 2:
Figure 1 MessageML Code
Figure 2 MesageML Display
Note: When the form is submitted, the new lines will be sent to the bot as a "\n"
Note: Refer to the article found here for further information