The World editor is a different game mode for Mashinky, which allows shaping of the game map at large, placing towns, industries, trees and infrastructure freely as players see fit. Players can create their own maps to play on and share them with the community. Maps can be randomly generated by the game then edited by the player, imported from a heightmap or fully handmade from a flat surface using the World editor's tools.
Making a map
Importing a heightmap
For use in-game put a 24bit bmp file in the heightmap folder: Steam\steamapps\common\Mashinky\heightmaps. Mashinky will only use the red channel for heightmaps but a greyscale image should work just fine.
A good site for getting zoomed-in real world heightmaps is Terrain.party.