I'm in this room and the objective is to get all the cubes on the lights, when I move them with the magnet buttons to smaller white cubes travel faster.
First, extrude both red blocks completely. You want to end up with the blocks in a configuration like the following (not to scale)
You should start by dividing the blocks with the top two above the lower red block and the other two below it. Then it took me a lot of moving with all four of the magnets to get to the above configuration. You can change the relative positions of the small and large blocks by taking advantage of the fact that the small blocks move faster. You can move a pair of blocks closer together or farther apart in the vertical direction by putting one against the red blocks and using the correct magnet to pull the other.
Basically, after dividing the blocks by the lower red block, you should have something like
If you activate the bottom magnet for the right amount of time, you should get something like
Then by activating the magnet at the right for enough time, you should get something like
Then activate the top magnet to get
Finally activate the left magnet to bring the blocks to the original target configuration, and then activate the right magnet to move them all into the lights.
This exact sequence of moves may not be enough to get all of the blocks in the correct positions, but the general strategy of using the speed difference to move the small block around the big one does work.