You can select a different origin upon creating a new scenario. I'm doing it differently. Open an existing scenario, then use the 2D map and Ctrl+LMB on your desired location then click the arrow in the compass box to teleport you there. Select the Scenario marker and place it where you want your scenario to start. You will be asked if you want to save changes to the current scenario - just press No and your new scenario will open. This way you have full control of your scenario marker position.
