I don't think so.
It's neither a hiragana nor a katakana nor one of the Kanji with three strokes, even when flipped (since saw-wrists baddie cut the door from the outside).
Furthermore, considering the episode's context (Batman is about to ask Corso more questions, the tension rises up), it's not too far-fetched to think there isn't much more meaning than the bad guy needing to kick that door fast. And it kind of works, as the horizontal cut enables saw-wrists baddie to punch the upper part of the door, then thrust his whole body into smashing the lower part.
As far as I can see, the gang doesn't have a custom symbol, so it's probably not that either.