This is what it looks like:
You can access it from the toolbox menu in TTD.
Here you can choose transparent or regular, "TTD style" station signs.
This sets the width of the train depot windows.
When enabled, this means everything in a depot outside the main train list area will act like the trash bin. You can then sell train vehicles by moving them onto the title bar for example.
Save these settings with the current game. Only works if "saveoptionaldata is on".
Remove these settings from being save with the current game.
Save as default
Make these settings apply to all games which haven't had settings saved with them.