Example CircuitBoardExample.cs
This example shows how to use a traversability filter function to generate paths like on a circuit board.
I.e., paths that do not share any node. The image below shows a test case when using the script to calculate 4 paths on a small grid. The visualization of the paths has been improved manually using an external photo-editing application.
The code has intentionally been left simple, so very little error checking and special case handling is done.
Note that finding paths on a circuit board in an optimal way is a very hard problem (NP-Complete). For further information about that, see https://en.wikipedia.org/wiki/Multi-commodity_flow_problem.
Attach this script to any GameObject and fill in the 'items' array with the start and endpoints of each path. 
TraversalConstraint using UnityEngine;
using System.Collections.Generic;
using Pathfinding;
public class CircuitBoardExample : MonoBehaviour {
[System.Serializable]
public class Item {
public Transform start;
public Transform end;
}
public Item[] items;
void Update () {
var blockedNodes = new HashSet<GraphNode>();
// Calculate all paths in sequence.
// It is important that they are not calculated in parallel
// as we need to make sure that the paths do not visit the same nodes.
// The result may vary significantly depending on the order in which
// the paths are calculated.
for (int index = 0; index < items.Length; index++) {
var item = items[index];
// Create new path object
ABPath path = ABPath.Construct(item.start.position, item.end.position);
path.traversalConstraint.filter = (GraphNode node) => !blockedNodes.Contains(node);
// Start calculating the path and put the path at the front of the queue
AstarPath.StartPath(path, true);
// Calculate the path immediately
path.BlockUntilCalculated();
// Make sure the remaining paths do not use the same nodes as this one
foreach (var node in path.path) {
blockedNodes.Add(node);
}
// Draw the path in the scene view
Color color = AstarMath.IntToColor(index, 0.5f);
for (int i = 0; i < path.vectorPath.Count - 1; i++) {
Debug.DrawLine(path.vectorPath[i], path.vectorPath[i+1], color);
}
}
}
}