i have some documents about finished exams such as biochemistry that i would like to move from my main knowledge base to my local knowledge base, since i don’t need those flashcards and info anymore.
i can’t just hit ctrl+A ctrl+C ctrl+V, because those are a lot of information, and i can only select one rem at a time with ctrl+A 
i tried the extract feature but it’s no use,
That sounds like a bug, ctrl+a once should select text in the rem, twice the actual rem, thrice all rem in the document.