side='previous',  -- experiment; you can unroll from a side thread and lose the current note

Edge_list = {'previous', 'next', 'child', 'parent', 'cross'}

Edge_list = {'previous', 'next', 'side', 'child', 'parent', 'cross'}

    'rename link ___ (to) ___ (some other label)',
    'clear link ___ (use with care! ignores opposite link)',

  elseif cmd == 'rename link' then
    command.rename_link(args)
  elseif cmd == 'clear link' then
    command.clear_link(args)

  plan_draw()
end
function command.rename_link(args)
  local from, to = args:match('(%w+)%s+to%s+(%w+)')
  if from == nil then
    from, to = args:match('(%w+)%s+(%w+)')
  end
  if Cursor_pane.col < 1 then
    print('no current note')
    return
  end
  local pane = Surface[Cursor_pane.col][Cursor_pane.row]
  if pane == nil then
    print('no current note')
    return
  end
  print('renaming link', from, 'of', pane, 'to', to)
  if Cache[pane.id].links[to] then
    print(('%s already has a %s note'):format(pane.id, to))
    return
  end
  local target = Cache[pane.id].links[from]
  local from_opposite = Opposite[from]
  Cache[pane.id].links[to] = Cache[pane.id].links[from]
  Cache[pane.id].links[from] = nil
  if Opposite[to] ~= Opposite[from] then
    if Cache[target.id].links[Opposite[to]] then
      print(('target %s already has a %s note'):format(target.id, Opposite[to]))
      return
    end
    Cache[target.id].links[Opposite[to]] = Cache[target.id].links[Opposite[from]]
    Cache[target.id].links[Opposite[from]] = nil
  end
  schedule_save(pane)
  stop_editing(pane)
end
function command.clear_link(rel)
  if rel == nil then
  print('specify a link to clear')
  return
  end
  if Cursor_pane.col < 1 then
    print('no current note')
    return
  end
  local pane = Surface[Cursor_pane.col][Cursor_pane.row]
  if pane == nil then
    print('no current note')
    return
  end
  if Cache[pane.id].links[rel] == nil then
    print(('%s has no %s note'):format(pane.id, rel))
    return
  end
  print(('clearing link %s of %s (used to point to %s)'):format(rel, pane.id, Cache[pane.id].links[rel]))
  Cache[pane.id].links[rel] = nil
  schedule_save(pane)
  stop_editing(pane)
  refresh_pane_height(pane)  -- just in case this is the final link