This is the one thing I find too fiddly to use built-in character sheets for...too many clicks and mouse movements to get what I need done. I've tried journal notes, and using the strikeout to cross them off my list. It's not ideal, but it does keep the notes in game. Again, I feel like it is too many steps. Have you tried using a deck of cards? I haven't tried it myself, but a "spell card" for each spell you have memorized put into your hand might work well. Simply play the card when you spend the spell. Again, I haven't tried this myself, and am not sure how much space it takes, but it sounds to me like it might work well you. Unfortunately, I think the GM is the only one that can make new decks or cards, so this might not be something he is willing to do for you.