SnowRunner™ Editor allows you to create custom maps for the game. Using this Editor you can also view your truck mods and ensure that they contain no errors.
The guide for this Editor in the PDF format can be downloaded from here: Binary.modcdn.io
Or, you can open this guide directly from the Editor, by selecting Help > Guide in the main menu.
NOTE: SnowRunner™ Editor and ability to play on custom maps created using it are currently available only on the Public Test Server (PTS) version of the game. For more details on the PTS version of the game, see Forums.focus-home.com.