We’ll take those things into account and work on improving our documentation in the areas you cited. What were the specific issues you had with the documentation regarding 1 (Add media), 2 (Create items) and 3 (Associate reference images to items)? We’re aware that the documentation for dynamically adding content to items is incomplete and will improve it soon.
As for the issue with the Item saying “The scene is not yet generated” it is in fact related to the Content Editor, without opening it and rendering it, we can’t generate a preview which also takes into account the position of the camera. We’ll also review the issue with returning a String instead of a proper JSON object. Which of our Management API libraries are you using?