I have created a solution that takes a 3D GridMap from Godot and uses it in the libGDX framework.  

libGDX unfortunately does not come with a 3D Editor, more importantly, it does not have any 3D grid editors like libGDX has for 2D tile sets.  

Since Godot has a simple GridMap node that allows you to quickly design and create a 3D world using 3D grid tiles, I made a solution that allows you to design your world in Godot and use it in libGDX.

Test the demo in your browser: https://antzgames.itch.io/libgdx-gridmap

Video: