I have a superliminal run that I did through livesplit but I've manually stopped the time between loading screens. Is there an autosplitter for the game I could use? If there is, where could I find it? And how would I transfer that into the video? (Since I've recorded the video already using livesplit) here's the video for reference

If you're playing on PC, you can use the autosplitter that is integrated with LiveSplit. When you go to Edit Splits, there should be an option to activate autosplitter. If you're on console, then there unfortunately is not an autosplitter.

Thanks, is there a way to incorporate that in the video I've already made? (Since I can't really edit the video and I've already recorded it without the autosplitter)

No, unfortunately if you don't have a timer shown the whole time, it's too late after the run. It has to be connected to the in game timer