I often use it as comment text to be saved with a preset. With a certain setting of your patch, type in the textedit a comment to that setting and save it together with the rest in a preset location.
The reason I am reading this post was to find out how to bang the content of a textedit box into a message. That way several messages can be saved in a dedicated preset object. Very handy to browse a preset with stored messages and bang the textedit box when showing the choosen message so that the message text goes via the route object into the right inlet of the message box.
I am sure there are enough other handy uses