I've installed the Addin. I can see a menu bar item that says "Options". I can access that screen. However, I can't get to the Builder screen for the Msgbox, or other items. How do you get to the actual screens?
I have checked the official page of the software and the MsgBox Builder is listed as being available which means this is either an issue or the software has bugs. I recommend installing the latest version of the software using the following link: http://www.avenius.de/en/?Products:IDBE_Tools
On that page you can also check the MsgBuilder screen to see how does it look like.
Secondly, if you still have issues after this, contact the developer using the following form: http://www.avenius.de/en/?&mailform