The good news is that you have not missed anything to this point. The editor is still in closed Beta testing the hopes are now that it should not be too much longer for the editor to be released.
3rd party is testing/learning to work with TSW editor in closed Beta. It will take time, but changes in 2020 edition signifies that editor should appear ... Read last STUDIO UPDATE 04/2019 https://live.dovetailgames.com/live/train-sim-world/articles/article/april-studio-update
I can not wait. As soon as the editor arrives I'll start buying the addons again. I have already set aside € 250,00 in my PayPal.
Hopefully the editor, which should've been released a while ago (yes, I am one of those players) will incentivize 3rd party devs to make routes that are actually around the world instead of 3 countries.