When you invoke this command from the BUTN menu, it prompts you to click on a field. It then places a separate Hiliter button over each line of that field that contains text. It skips blank lines. In order for SmartSlides to know accurately which lines these are, it is essential that each line of text in the field end with a carriage return, i.e. that no lines be word-wrapped.
The command button works the same way, except that it omits the prompt.
This feature is handy when a field contains a list of items, one to a line, and you want to be able to hilite each item as you discuss it. It saves a lot of time compared to creating each separately and lining them up "by hand".