How do I make navmesh generate on very steep surfaces?

is there a setting somewhere that defines slope angle?

Yes there is. Build your navigation and find the recast navmesh sth. object in world outliner. It has a setting called Agent Max Slope. That’s the one you want.

I found the parameter but changing it doesn’t do anything.

Have you rebuilt the navigation? It works on my end.

Yeah I have. odd. I’ll errr… dunno. I’ll have a tinker.