I've also inadvertently pushed swimming entities into the ground by dropping stuff on them, but this is the first time I've seen a super useful exploit in this game.
Unfortunately, this seems like it's a very specific case that can't be replicated in many other levels, but if I find other levels with good clipping methods I'll post them here, and I encourage others to also experiment with clipping.
It seems like you can clip into ceilings by creating a fan, dropping it on Maxwell such that it blows upwards, then using a solid object in the same fashion as in the above post. However, it is incredibly finicky, and so far I haven't found much use for it.
Additionally, you can attach a starite to a rope, cord, floss, leash, etc., and attach that to a metal gate that is blocking it. Depending on the circumstances, this can allow you to cheese plenty of levels.
Through some accidental research, I have found that it is possible to farm money using a custom level created in the level editor.
There are some caveats to go along with this for speedrunning, namely that there is nothing stopping you from playing levels created on another save file with access to
