The following will add a vertical scrollbar to the original request ( = the first message that the customer sent ) if it is very long.
<style> div#original_request.conversation_thread div.conversation div.commentbox.private-note { max-height: 60vh; overflow-y: auto; } </style>
Note: 1vh = 1% of the height of the viewport ( the browser window size
). Thus, a good max-height is usually 50 to 70vh but depends on the size
of the monitors of your crew and preference.