Can we add a new category about the level "Train rush" (Act 4) of the Chapter 2 ?
He is so fun to speedrun :D
Go to the level leaderboard for Battle of the Birds - Train Rush. This is an individual level run, not a new category. Also, be sure to turn on skip cutscenes and more importantly the in-game timer in the Game Options, or else your time can't be accepted as it violates the rules. Hope this helps!
The category already exists: https://www.speedrun.com/ahit/Battle_of_the_Birds_-_Train_Rush
Also, what OnlyFriendlyGuy said. Skip Cutscenes On and In Game Timers On in the options.
In the console, type "enablecheats" and then "fullyrestartlevel". This will cause the timer to be late on restarting, so you'll lose a couple seconds, so it's best only for practice. If you're on the modding branch, you can use the RestartIL mod available.