I usually find that Quicken is most useful when you need to take your action to Disengage/Dash/Hide
I can’t see myself using metamagic points for that, either. Is that something you used it for a lot in BG3?
I'm speaking mainly from tabletop experience. Disengage can help your caster to attack at normal instead of disadvantage and/or run away from the enemy in order to not die and to help keep concentration. But most of the other important Actions in BG3 have been changed/not implemented.
In BG3, Hide and Potions are bonus actions, so obviously quicken is not needed for those. Dash will basically never be useful for spellcasters in BG3 because of the smaller maps. Oh and I completely forgot to mention Dodge. Dodge (+ mirror image & shield) is pretty powerful in tabletop against attack rolls and Dex ST effects; get in the middle of combat, quicken a powerful spell and use your action to Dodge, then shield any hits that get through! ...but of course Dodge doesn't exist in BG3.
