I recently started playing DnD5E (the starter campaign Lost Mines of Phandelver), and read about the memorization of spells.
And even more recently I started playing Baldur's Gate 3.
In BG3 I noticed that I can put spells on and off prepared list for both Wizard and Cleric at will (except in combat). So I could cast Mage Armour, then replace it in memorized spells with something else (of course 1 lv1 spell slot would still have been expended).
As I understood from earlier answers here, this is against DnD5E rules, which stipulate you can only change memorized spells once after long rest.
Since we're all beginners in DnD5e and it's our first campaign, could you please advise whether it would be OK to adopt the BG3 method of memorization in the campaign, and if not - why not?