This plugin helps you to set your permalinks by using custom taxonomies just like you use %category% or %postname% in your permalink structure.
I was requested to support sub-taxonomy just like WordPress supports sub-category in URLs. For example if you use %category% in permalink structure and a post has sub-category, %category% will be replaced with 'parent-category-slug/child-category-slug'. In order to do similar things with custom taxonomies I tried many things but the solutions was getting complicated just because of forward slash (/) character as separator. So in order to keep things as simple as possible I used plus (+) character to separate child and parent custom taxonomies. I know this is not what most of us want but still it solves sub-taxonomy problem. I will fix this as soon as possible. Also I used a limit of three parts per replacement. So a custom taxonomy structure tag can be replaced with 'grandparent-slug+parent-slug+child-slug' at the max and won't show 'great-grandparent-slug' even if present.