Here's the documentation on how to use the built-in track editor.
A Sheets document with the best times for every track, plus statistics and rules for submission.
Times must be submitted in the Team Scripted Discord.
A Paper plug-in that allows you to save ghosts, watch replays, and race against staff ghosts.
A tool allowing you to transfer your Time Attack data and cheat codes between Sprint Racer worlds of any version. (Windows)
If you're planning to publish custom tracks, make sure the regions you want to use are available. This will help in avoiding file conflicts when people install your custom tracks.