It's not clear what scenery you are referring to. Assuming you are referring to KSDF, because you linked to a thread in the KSDF section, I assure you that one DOES have a "Enable Ground Traffic" on the YouControl menu of the SCENERY.
The issue is, from your screenshot ( pardon me if I cannot immediately recognize which FSDT scenery is, assuming it is an FSDT scenery in the first place...), you called the GSX menu, not the scenery YouControl menu.
- If a scenery has a YouControl menu ( most of the FSDT sceneries have it ), it's by default set on CTRL+F12, unless you changed it. In this case, the first page of the menu should have two options: calling the YouControl menu of the scenery or calling GSX.
- If a scenery doesn't have a YouControl menu ( all default or 3rd party ), by default, pressing CTRL+F12 will open the GSX menu, uUnless you change it.
- By default, if you press CTRL+Shift+F12, it will always open GSX, regardless if the scenery has a YouControl menu or not. Unless you change it, of course.
So, if you don't see the YouControl menu, either you are on a scenery that doesn't have one, or you changed the key assignments to have GSX on CTRL+F12 and YouControl on something else. You can check your key assignments under the Couatl Settings -> Key Mapping menu.