I think this could be a solution. Unfortunately the documentation is a bit outdated: Transition Rules in Unreal Engine | Unreal Engine 5.1 Documentation
You can see they didn’t have the Blend Graph when they made the documentation 
* Edit: This might not be the case since they didn’t set the blend to custom, but I guess that’s not really the point I was trying to make.*
My follow-up question is, how do you apply logic in the blend graph? I’d like to have Idle -> Walk, with the transition rule handling all 4 of my WalkStart directional animations by determining the direction (a variable) the player is moving.