The Scenario Editor in OpenTTD is a tool which allows you to create your own scenarios for OpenTTD. It can edit and create scenarios in all four climates. It allows the landscape to be randomly generated, and towns to also be placed randomly, allowing scenarios to be made with relative ease.
The scenario editor was not present in the original Transport Tycoon of 1994, was introduced in its World Editor expansion pack. It stayed in TTD, and was therefore in OpenTTD from the start, and from then on undergoing many updates. It is possible to expand towns to their largest sizes possible. The scenario editor can be started with the -e option.