How to save a navigation mesh / source geometry to disk

Godot Version

4.3

Question

I am baking a quite large navigation mesh, consisting of up to 5.000 polygons. Since baking takes quite a long time, i would like to store the generated sourceGeometry data or the resulting navigation mesh to disk. The help only gave me a line, stating that this is possible, but i have no clue on how to do this. Any help? Thanks a lot.