如何在jsTreeR的菜单列表项上添加悬停文本弹出窗口？

问：

我一直是 Shiny 内部 jsTreeR 包的活跃用户。运行下面的骨架代码时，顶部会显示一个可拖动选项菜单，用户将这些项目向下拖动到标有“>> 拖到此处<<”的目标列表，以生成自定义的顺序标记列表。将鼠标悬停在这些菜单项上时，是否可以构建带有解释性文本的悬停弹出窗口，如下图所示？这怎么能做到呢？

一旦元素被拖动，就不需要相同的悬停弹出窗口。仅适用于位于顶部“菜单”部分中的元素。

法典：

library(jsTreeR)
library(shiny)

nodes <- list(
  list(
    text = "Menu",
    state = list(opened = TRUE),
    children = list(
      list(text = "Dog",type = "moveable",state = list(disabled = TRUE)),
      list(text = "Cat",type = "moveable",state = list(disabled = TRUE))
    )
  ),
  list(text = ">> Drag here <<",type = "target",state = list(opened = TRUE))
)

dnd <- list(
  always_copy = TRUE,
  inside_pos = "last", 
  is_draggable = JS(
    "function(node) {",
    "  return node[0].type === 'moveable';",
    "}"
  )
)

mytree <- jstree(
  nodes, dragAndDrop = TRUE, dnd = dnd,
  types = list(moveable = list(), target = list())
)

script <- '
$(document).ready(function(){
  var LETTERS = ["A", "B", "C"];
  var Visited = {};
  $("#mytree").on("copy_node.jstree", function(e, data){
    var oldid = data.original.id;
    var visited = Object.keys(Visited);
    if(visited.indexOf(oldid) === -1){
      Visited[oldid] = 0;
    }else{
      Visited[oldid]++;
    }
    var letter = LETTERS[Visited[oldid]];
    var node = data.node;
    var id = node.id;
    var index = $("#"+id).index() + 1;
    var text = index + ". " + node.text + " " + letter;
    Shiny.setInputValue("choice", text);
    var instance = data.new_instance;
    instance.rename_node(node, text);
  });
});
'

ui <- fluidPage(
  tags$head(tags$script(HTML(script))),
  fluidRow(jstreeOutput("mytree"))
)

server <- function(input, output, session){
  output[["mytree"]] <- renderJstree(mytree)
}

shinyApp(ui, server)