Thank you @Jeremy! I am not so bothered about the single session but more about the composition of my overall studying material. What I am thinking about is to create a mix of studying material, that I can review in one daily session. Definition and pinyin of all vocab, writing for HSK1 and 2 (possibly 3) vocab only. Reason being that for now I want to limit handwriting to core-vocab (possibly the around 500 characters suggested by @SkritterOlle at HackingChinese). I could obviously use Skritter only for writing practice and other apps for definition/pinyin, but preferably I can do it all in one app.
The problem I encountered yesterday seems to have been caused by my mistake, though: I had already “learned” the decks I wanted to restrict. It seems that if I restrict studying to definition and pinyin in the web-interface before “learning” a deck, it will only include the desired cards. For the future, I would find it helpful to have these choices in the app itself. Also, I do not know what I have to do if I want to add writing at a later stage. Will I have to “forget” and “relearn” the decks?