Don't use the character sheet. Take advantage of modern printers to provide a clear hierarchy on more paper to make for faster lookup. More information density actually increases lookup time. A larger sheet with better headers will reduce lookup time relative to a dense sheet.
First, there's no limit to space. While photocopied pages have limits as to space, we live in a computer mediated age. Unpack your character sheet onto multiple pages. Make each page relate to itself with a clear header. Copy and paste rules that you frequently will want to refer to onto the page itself. Include sections of the character sheet on each page as a mnemonic.
In my classes, however, one of the test preparation strategies that I recommend is the creation of a cheat sheet by hand. While transcribing this into a computer form is commonly done for legibility, the act of writing, I have observed, helps my students remember, if only because it takes more time.
Make cheat sheets for every aspect of your character. Highlight the cheat sheet with many different colours, and colour your character sheet (and expanded character sheet) with the same colours. This is to create an easy-to-check correlation, i.e. blue parts of character sheet = check blue parts of cheat sheet.
Between colour indexing, clear headers on your expanded sheets, a page full of "key-value pairs" for frequent numerical lookups by name, and a hand-written cheat sheet to internalise the mechanics of your character, you won't need to rote-memorize your character sheet: you'll understand it instead.
If you absolutely need to rote-memorize, use Anki, as it is a highly recommended flash-card content memorization app. Take portions of your character sheet and put them on flash cards. Then, the correct answer is the label of the category of the character sheet. It's effective because:
It’s like flashcards, except that it uses spaced repetition to remind you of your cards at the optimal time so that you retain the information. There are loads of publicly available decks that can help you learn stuff. You can also make your own decks.