Patrick 
Has successfully completed the online course IntroductionHi Armin,
thanks for your detailed explanation! I’m not allowed to watch the video at the moment because I have to finish the previous lesson first. I’ll watch it later!
I updated and re-uploaded the test project for you. Hopefully this gives you a better understanding of my problem with data binding in TabContainer and the content of its items.
To reproduce case 1 (client side business object only), add 1-2 TabItems, delete one and then add one again. A duplicate ID error message follows.
For case 2 (script only) the item is missing the actual content which I can’t add using the addContent method even though the aggregation is set in the widget settings. If I could do it, it wouldn’t have a binding anyway, right?
Case 3 (script and client side business object) is my attempt to force the content via the binding without generating an ID error message.
Thank you for your time!