I am trying to start to speedrun GTA and have just got LiveSplit. I have it on the left side of my screen. But if I aim too far left and shoot it clicks onto LiveSplit disrupting the run. I have tried using Lightnat0r's cursor jail but it doesn't work for me.

maybe u wanna try using ur phone as second monitor and letting run livesplit on it if you dont have a physical second monitor. software for this could be spacedesk https://spacedesk.net/multi-monitor-app-virtual-display-screen-software-video-wall

what you could also do, as the hotkeys for LiveSplit work even if you can't SEE LiveSplit, is record with LiveSplit in the background, like running the game on fullscreen. if you record with OBS and have the right layout, the timer will still appear for the video/livestream, even though you can't see it. all the hotkeys still work, so set your hotkeys as buttons that you'll never use in GTA, like Numpad+ and Numpad*

LiveSplit updated recently and apparently has an option to prevent it from getting clicked on.

just select the "ignore mouse while runing and not in focus" option in the edit layout , layout