Trying to make a 2.5D game with 3 lanes.

Hey guys,
I want to experiment a random idea by making a 2.5D game with 1 lane split into 3 lanes. Where the player character sits in the middle lane on the let side, and the monsters fill in the other 3 on the right side. but im having some navmesh issues.
does anyone have any links or resources on how to go about doing this?
I thought I could separate the 3 lanes with an invisible Collision wall, and then give the monsters an ability that allows them to switch lanes at the cost of energy. but its hard to find any resources on how to actually go about coding this.
omegleshagle
Thanks

You could probably add the notion of “lanes” to my 2.5D demo package (source and project linked in comments). Something would either be on the given path, or nearer or farther from it depending on its lane number.

https://www.youtube.com/watch?v=BtT1N1lzFns