Saw in another post a problem with Navigraph FMS  Data Manager and IXEG B737. I figured it out- maybe not major science, but at least for me it works! In the Navigraph FMS Data Manager I mapped the IXEG B737 to the following folder: .....X-Plane 12\Aircraft\ X-Aviation\IXEG  727 Classic Plus that's it!  The Navigraph FMS Data Manager set the files in the correct folder for X-Plane 12.