paths = ['Rechnung', 'Rechunung/Ja'] // hier sind deine paths als array
data = []
map = {}
for path in paths
  head = ''
  tail = path
  if path.indexOf('/') isnt -1
    head = path.substring 0, path.lastIndexOf '/'
    tail = path.substring path.lastIndexOf '/'
  next = {text: tail, children: [], ...}
  if head
    parent = map[head]
    parent.children.push next
  else
    data.push next
  map[path] = next