Is there a stud multiplier in LEGO Batman: Legacy of the Dark Knight?
Yes, but not as a red brick. Stud multipliers come from skill-tree upgrades and WayneTech Chip purchases at the Batcomputer.
Unlike the classic LEGO Batman trilogy where stud multipliers (x2, x4, x6, x8, x10) were red-brick cheats, Legacy of the Dark Knight folds them into the skill tree. You earn WayneTech Chips from the 200 WayneTech Caches and spend them at any Batcomputer / workbench to upgrade gadgets and stack stud bonuses. Red bricks in this game are purely cosmetic skin/color variants for suits and vehicles.