To stack or unstack icons on Taskbar in Windows 11 ... you can select any icon and place it on the Taskbar like a 2×2 or 3×3 block. In case you want to revert the change or ungroup icons ...

So you rotate the blocks, find the proper orientation to make them all fit and complete the stage. In another stage, you have to stack all the blocks vertically at just the right angle to balance ...