According to this KB document (Can we send Manual Notifications in HTML format? - CA Knowledge), in CA Service Desk Manager 17.1 we still can't send manual notifications in HTML format. Even the Manual Notification Template don't have an HTML editor.
I think this feature meets a real business need since e-mail messages are an important way in which Service Desk analysts can get in touch with the customers and end users.
This idea was first proposed in 2012 (HTML formatting for Manual Notifications in SDM 12.6.) and then in 2014 (HTML Support for manual notification ). In both cases, the idea hasn't attracted much attention and their status is "Not planned". Maybe it's time to reconsider the idea?
Thanks in advance,