Have you heard of phonetic components? Many kanji have parts that indicate a reading and can be used to often know the reading of even kanji you haven’t seen before. Hate to say it again, but there’s a script for that…
Definitely don’t keep them on the side. This could hurt your long term retention since you wouldn’t be properly reinforcing the kanji. You should never be more than half a level to a level behind on vocab. If you ever find yourself more behind than that, it probably means you’re misusing one of the scripts and/or leveling up too fast.