Oh, nice! Someone altered Ortho4XP to spit out scenery tiles compatible with FSX and P3D.
If you download the lot from the top entry of https://github.com/stackTom/Ortho4XP_FSX_P3D/releases (and trust the binary I guess) then the windows .exe will be in the dist/ folder. You’ll also need the ‘resample.exe’ from the FSX/P3D SDK to make this work (found on the media disks or online, not included with Steam FSX).
The downsides are that it only does daytime tiles so far, but the upside is that it’s open source so updatable and likely to improve.
Bugs and comments back to author at:
I need to put back on FSX to try it out, but I’d imagine if you can work regular Ortho4XP then you can work this.