in the Lower Thirds layer, the editable text fields of Title and Subtitle have just 1 line.
I luckily discovered that if you click alt+enter you can indeed create a new line of text.
but the text entry form remains just one line.
So the good news is that I can successfully design lower thirds and being able to write text in more than one line, but the bad news is that the UI does not reflect that and I’m not able to see all my text in the editable field.