hey, thank you for playing! there's currently a prestige unlock that lets you assign cherubs using right-click. it may have been hidden though (we just changed it so you can preview the unlocks sooner).
we do agree it's a bit weird to assign cherubs in general. we've just added a quick notice in-game to let folks know that you can zoom in with the scroll wheel/new - + buttons on-screen. there's also an upgrade at the Dorm to carry multiple cherubs at once!