To Change your Scenario in Space engineers and easily apply a list of mods and any other configuration changes, the easiest way is to generate a new world. This is due to a large portion of the config only applying when a world is generated. To generate a new world, simply navigate to the world management tab in your clanforge control panel and select "Reset world" This will delete the current world (Please make sure the server is offline before making any changes!) When you start the server up again, it will generate a new world based off the server config found in the edit profile>configs section of your clanforge control panel.

E.g. Scenario can be changed as below

Another popular setting to be changed is asteroid amount, this is chosen from a 0-5 list (see below)

Any changes Wanting to be made to an Existing world, e.g. Adding mods or changing scenario and many other settings will need to be changed in the sandbox.sbc file for your current world and reuploaded.