If you plan on getting every single spell in Baldur's Gate 3 as soon as possible, hold off for now. It turns out that if you spend gold to add scroll spells to your permanent collection, you can run into a bug when levelling up. Part of the process demands you pick a spell, but if you have them all, you can't pick any, so you'll get stuck without a way to follow through or quit the menu, losing all progress since your last save.
Reddit user Yourigath shared this discovery on the Baldur's Gate 3 subreddit last night, attaching a screenshot of the level-up screen that shows no way of hitting the accept button since they have "choices pending" (thanks, PC Gamer). The choices pending in question are two spell slots they have to pick, which they can't.
The only way to fix this right now is to download a mod "that lets you have ritual casting like in actual Dungeons & Dragons (you don't need to prepare the spell, as long as it is in your book you can ritual cast it)." Once you have it up and running, save, level up, delete it, and save again. Voila. Alternatively, you can swap classes, but if you try to respec back into a wizard, you'll get stuck again.
Yourigath has flagged this issue with Larian Studios so it's only a matter of time before it's patched. Until then, if you know every single spell in the game, you'll have to hold off on levelling up unless you want to faff around with mods or respeccing, which will lock you out of the wizard class anyway.
Alternatively, you can hoard the scrolls and wait until the bug is gone. You can still cast them or just lock them away somewhere safe until later, committing them to memory so you can finally become an all-knowing magical powerhouse.
In the meantime, fans are calling on Larian Studios to add the option to change character appearance on the fly mid-game. As it stands, you can only customise your main character and Guardian at the beginning of the game. Once you hit play, there's no going back. Interestingly, this wasn't the case in Larian's last game, Divinity: Original Sin 2. There you can use the green mirror to not only change how you look, but how your entire party looks. But if I'm honest, I wouldn't change a thing about Karlach and Gale.