Hi guys,
thank for your answers.
@Ingo
Nice to read you again. We met each other at a SAP executive training in Walldorf in 2013, but i am afraid, you don't remember 
Regarding my issues:
After a lot of testing and debugging, I have found some very interesting aspects. My coding looks in the initial state as follows:
TEXT_USER.setText("Hallo " + DS_KOA.getInfo(().user + " - Herzlich Willkommen!");
TEXT_DATE.setText("Aktuelles Datum " + APPLICATION.getInfo().dateNow);
// Here is a blank line in my Startup script
DROPDOWN_KOAR_BM.removeAllItems();
var array = Bookmark.getAllBookmarks();
array.forEach(function(element, index);
{ DROPDOWN_KOAR_BM.addItem(element.name, element.text);
});
INPUTFIELD_KOAR_BM.setValue("");
I found out that the system has got problems with blank lines within the coding. In my case this means that the whole coding after the blank line will be skipped. I assume this as a bug.
If I remove the blank line, the system almost works as expected. Almost, because the application alert is still not working. At this stage I don't have a clue why
Best regards and TY,
Karsten
P.S: The coding within the BackgroundProcessing was meant to update the drop down menu. But, i guess, it is not required.