I am currently only capable of turning NHD shapefiles (NHD Area and NHD Waterbody layers) into water vectors. I was fine with the default P3D/FSX streamline, but lines sit on top of polygons so I had to find a way to turn the NHD Flowline data into a four-meter-wide poly. The water shapes look much better in the sim, but I haven't been able to get the shorelines to happen yet -- I'm sure I'll get somewhere by revisiting your always helpful posts, which I have to do often. Plus, the water texture probably isn't nearly as good as it should be, since I am using the Legacy No Flatten GUID as I can't figure out where to point ScenProc to find embedded "Z" elevation data for vectors.
Here is what I would like to do regarding water (and what I have so far is available to the FS community as freeware on my website):
1.) Turn streamlines into polys
2.) Import waterbodies and streams into sim
3.) Add shorelines to all
4.) Use non-legacy water GUID
5.) Eventually change waterclass for different types of waterbodies
Step 1 is pretty easy, I just figured out a way to do number 2 (but there may be much better ways), 3-4 I am stuck on and 5 has a lot of higher-priority stuff ahead of it. I hope I made a little more sense, and thank you!
Perhaps a review of the info in this prior thread discussing SBuilderX options, might still be helpful to consider as an alternative to the more complex QGIS workflows ?
BTW: See my EDIT in the above linked post, to point out an easily overlooked SBuilderX.ini file parameter value described by SBuilderX author Luis Sa' in a post on the "Closed Line" function.
Also, note that the possibility for a reverse work-flow in SBuilderX to convert 'Closed Lines' to Polygons is alluded to here: