I'm not aware of anything now - I think it might not be very hard to do.
You should be able to get a list of selected objects from the SelectionManager. Step through that list and check if each entity is a note object. From there, you could sort them according to vertical position - I think this would be better than figuring out the selection order as it doesn't constrain the user to select notes in a sequence.
From there, you can step through each note and append the text to a string with a carriage return between each addition.
Finally, assign the string to the note with the highest y-position, and delete the rest of the notes.