If you're happy with a solid outline you could use the outline effect.
For a dashed line you'd need to calculate the outline from the intersection of the shapes. The canvas plugin gives a way to draw it after you calculate it, or you could use a tiled background for each edge.
It's not super trivial to calculate but a lot of solutions can be found online that can be adapted over.
What is this outline effect? Is this a separate effect altogether or is it an action found in Canvas?
Sorry but I have no experience using this plugin yet so I don't know where to begin