I'd also add that when Papers is closed and restarted, tabs from the last session should remain open.
I would add that this be possible also when, lets say, we are reading an article and on page 5 we decide to use the search function to find a word within the article, after seeing all the places the word appears via the search result list we can quickly go back to where we were reading in the article. I do this type of searching a lot, specially when coming across annotations and need to quickly find where it was used first in the article and see its definition. It would be helpful to quickly jump back to where I was reading.
The most frustrating lack of feature in the current iteration of ReadCube Papers. Please, please, please FINALLY add this feature!
Remembering the last read position is crucial!