Hello,
the template editor/templates are global. So if you add the message it will apear in each survey using this template. I'm not sure if that's what you want to do anyway, I just want to tell you so you don't run into problems.
Anyway, I marked the Template Editor with a red circle:
EDIT:
My Dutch is not very good but I think you already asked the question in the Dutch forum on
www.limesurvey.org/de/forum/dutch-forum/...emplate-editor#76592 . It's always best to ask your question at the english forum because there are more user.