I've already asked several questions in the forums, but I still feel lost. For every feature I want to implement, I have to come here to ask if it's even possible.
So, what I would like to be my last question: Is there any documentation around?
This will give you a lot of important infos.
But there is no official documentation for ExtendScript APIs. Therefore I recommend studying the PProPanel Sample:
I do recommend asking questions here. Especially if you dig into the ExtendScript APIs. Adobe´s Bruce Bullis used to be very responsive and supportive. Additionally, I started following these forums to help others since I know how complicated Premiere´s SDKs can be at the beginning.
In addition to Thomas' answer, you can also view all available methods and attributes via reflection using ExtendScript Toolkit application. When Premiere is running the attributes are populated in the Data Browser.