As also posted in the “Programming & Scripting” section after banging my head for a long time on this one, I’ve discovered that as you run your PIE session, the Enable Drawing flag is set to false. So the solution to this issue is to set the flag back to true WHILE THE GAME IS RUNNING. At that point the console command “Show Navigation” works as expected. As a bitter note, I haven’t found a way to visualize the custom agents navmeshes while in editor mode (ie. without the game running).
The reason for this behavior are beyond my current understanding of the engine, in any case, if there’s anybody from the Team listening, it’d be great to know what’s the procedure to follow to be able to visualize my navmeshes also in editor, same way you can do with the default navmesh with the “P” shortcut.
Bumping this since previewing nav meshes with custom agents is still not possible in 5.3.1 as far as I can tell. Custom agents seems to be really under documented in genera, getting it operational has been a struggle so far despite seeming like a pretty common problem many games would have.