I can't tell how to see the migration paths on the map. Is there a keybind or something?

They should be on by default. Theres a way to change the specific color, but they should be appearing. Do you have anything changing nauvis world gen?

And let me take a look

I added it to an existing save file, that's probably what happened

ah, yeah that would do it. I'm not sure how to get around that. because if I did allow it to show up on existing saves suddenly your whole factory would become damaged. let me add a note of this to the mod description.

Yeah I went and started a new sandbox file and it worked perfectly. Funny thing though, it looks like the code doesn't take note of any changes to the environment (notably turning land into water like waterfill or moat mode) which sometimes leads to the biters walking on water lol.

Yeah. I might look into adding a swimming animation. Biters crossing shallow water is intended brhavior but it does look weird lol.
Jesus biters

The thing is that it happens regardless of whether or not biters can already swim. Haven't tested but I think they could probably cross lava and stuff too. Not sure if there's a way to make what's code-wise technically a demolisher adapt its patterns based on changing terrain, but that's not my problem :)

I don't think any mods that add lava to nauvis do it in a way where lava becomes an issue.

If the player has a mod that allows biters to swim, these "biters" are just animations until they take 1 damage so youre totally right that they just walk across the surface. It gets tougher to animate each thing differently depending on its terrain. Maybe i could do something with run time scripting but I really wanted to keep the game as performant as possible (minimal runtime scripting) if someone has proposals please let me know! I may come back to this after I release my next mod.