Good idea, I'd considered adding costs to the nodes but not to the edges. Do you have a particular use case in mind? I'll have a think about it and maybe add it to the roadmap, thanks!
And for the edge nodes, let's say I use the "cost" field to determine the cognitive cost for any given task, I can more easily see which sub-task (edge) to prioritize if I want to get into "the zone" more quickly in an "intention"/project (parent node).