Service mode is more of a sandbox rather than like fixed missions or scenarios. In the main entry screen for service mode, click on your character. You can now use the map to spawn on any platform or listed location. You can also:

1. Click on a train
2. Click on 'continue'
3. Select a service

Scenarios have a back story and are more structured.

1. F12 saved to "C:\Program Files (x86)\Steam\userdata\1104364819\760\remote\1282590\screenshots"
2. Ctrl F12 saved to "C:\Users\bgmca\OneDrive\Documents\My Games\TrainSimWorld2\Saved\Screenshots\WindowsNoEditor"

The diffence is Ctrl F12 automatically removes the GUI for photos.