Skip the invisibleRelation property and uses for every edge the edges property of the
json node:

{
  "id" : "rst_0_4" // has to be globally unique
  "name" : "4"
  "edges": [{
             "annotation":["conjunction"],
             "to":"rst_0_4",
             "sType":"multinuc",
             "from":"rst_0_1"
             },
             {
              "annotation":["nonvolitional-result"],
              "to":"rst_0_4",
              "sType":"rst",
              "from":"rst_0_3"}]
}