Hi @Kubilay,
Thank you for your message and welcome to the forum.
Inter-App Audio comes with many limitations and Apple has released Audio Unit support quite a while ago, which can be more or less seen as their successor to IAA.
To learn more, please have a look at our dedicated Limitations of Inter-App Audio article. Algonside, we recommend to use Audio Unit apps where possible, which provide much more flexibility.
In this regard, please see how easy it is to use AU instruments and effects plug-ins with Cubasis in our Getting started with Cubasis tutorial.
Hope that helps!
Best wishes,
Lars