Sometimes I am making notes about something I am studying and it would look better if I could simply continue until the end of the study without having to continuously keep adding new pages.

I just need to create endless threads in order to record notes from daily checkins. I don't want it limited to a page per session or so. I can do that with a physical notepad. I'm baffled why this is not a feature in a digital notebook

Same here.
These days I am trying to sketch some mobile app interfaces. As these interfaces can be scroll up/down and left/right, an additional option to extend the width or length of the paper can be really helpful.

Would love that feature!

Same here. I use GoodNotes mostly for scribbles or low-res wireframes of webpages and interfaces and it'd be awesome if i could expand the paper i have down to the size i need.

I usually don't know the needed size when i start scribbling, so a function to expand the "artboard" would be awesome.

Yes I would like this for lists, otherwise I may not realise when a list ends.