I watched the video tutorials on creating a German train route using TSW Editor shown at Tutorial - Tutorial Series: Let's Build Duisburg-oberhausen Together | Dovetail Games Forums but I am very confused. Is it possible to create a simple route using flat terrain and Open Street Map overlay?
You can create a fictional route as well, yes. You don't need any SRTM (DEM) or Lidar files for that, because they contain the elevation profile for a real route. You also don't need the Google Maps (not Open Street Maps - unfortunately) overlay then, since this is only necessary if you recreate a real route. However what you need is a KML and a real source coordinate to create the route map and generate the landscape tiles still. When you have no elevation data, all what is generated are completely flat tiles on which you can build your own landscape using the Landscape Tools in the Editor.
How can I create KML file that can be imported into TSW5 Editor? How can I set real source coordinate?
How to create a kml file in Google Earth Pro as well as Using a real start Lat Long coordinate for your map can be seen in this video by DTG Lukas from around minute 13:50:
I tried to watch the video but I'm still confused. The video was for TSW4 Editor, not TSW5 Editor. I wish there is written instructions on creating a new route.
It is kind of complicated, that is for sure. I'm pretty sure the process hasn't changed in the TSW5 PC Editor though, so everything in that video should apply.
I created a new plugin, created new route, imported KML file, created new landscape or terrain, and tried to create Google Earth overlay but both the KML data and the Google Earth overlay don't show up. The video tutorials are not helpful. Any suggestions?
Not sure if this is properly documented anywhere, but one thing you should probably do is ensure that the latitude and longitude you enter for your plugin are +/- instead of E/W or N/S. When I started making my plugin I tried using a West latitude for Toronto ( 43.6532° N, 79.3832° W for instance,) the Editor was putting me at 79.3832° E (half a world away!), but -79.3832° worked. Not sure if that is the problem, necessarily, but it's one thing to check.
The processes did not change between TSW4 and TSW5 Editor. In fact, the TSW5 Editor only got the cooking functionality and a few fixes added. Nothing related to route creation has changed. Are you trying to replicate a real or doing a fictional route? That is important to know before. Because the wording of "flat terrain" in your OP suggested to me that you intend to create a fictional route.
I am hearing-impaired and captioning is turned on. I must have missed some steps when trying to create a route.
Don't worry. Noone understood the videos when watched (and listened) to for the very first time. The learning process comes with time.