如何在R Markdown中创建双重嵌套标签页？

好问题！默认情况下，R Markdown的原生.tabset功能只支持最多两层嵌套标签页——这就是你用<div>加四级标题没生效的原因。不过别担心，有两种靠谱的方法能实现你想要的三层嵌套标签页，我来给你详细拆解：

方法一：手动用Bootstrap组件构建第三层标签页（适配原生html_document） #

因为原生html_document依赖Bootstrap框架，我们可以直接用Bootstrap的Tab组件手动搭建第三层标签页，替换你原来的四级标题部分即可。下面是完整的可运行代码：

---
output:
  html_document:
    theme: paper
    highlight: tango
    number_sections: false
    toc: false
    toc_float: false
---
# Result Discussion {.tabset}
We will discuss results here
## Quarterly Results {.tabset}
This content pertains to Quarterly Results
### By Product
Quarterly performance by Products

<!-- 手动构建第三层Bootstrap标签页 -->
<ul class="nav nav-tabs" id="productCaseTabs" role="tablist">
  <li class="nav-item" role="presentation">
    <button class="nav-link active" id="caseA-tab" data-bs-toggle="tab" data-bs-target="#caseA" type="button" role="tab" aria-controls="caseA" aria-selected="true">Case A</button>
  </li>
  <li class="nav-item" role="presentation">
    <button class="nav-link" id="caseB-tab" data-bs-toggle="tab" data-bs-target="#caseB" type="button" role="tab" aria-controls="caseB" aria-selected="false">Case B</button>
  </li>
</ul>
<div class="tab-content" id="productCaseTabsContent">
  <div class="tab-pane fade show active" id="caseA" role="tabpanel" aria-labelledby="caseA-tab">
    Quarterly performance by Products in Case A
  </div>
  <div class="tab-pane fade" id="caseB" role="tabpanel" aria-labelledby="caseB-tab">
    Quarterly performance by Products in Case B
  </div>
</div>

End of section quarterly performance by Products

### By Region
Quarterly performance by Region

<!-- 同样构建Region下的第三层标签 -->
<ul class="nav nav-tabs" id="regionCaseTabs" role="tablist">
  <li class="nav-item" role="presentation">
    <button class="nav-link active" id="regionCaseA-tab" data-bs-toggle="tab" data-bs-target="#regionCaseA" type="button" role="tab" aria-controls="regionCaseA" aria-selected="true">Case A</button>
  </li>
  <li class="nav-item" role="presentation">
    <button class="nav-link" id="regionCaseB-tab" data-bs-toggle="tab" data-bs-target="#regionCaseB" type="button" role="tab" aria-controls="regionCaseB" aria-selected="false">Case B</button>
  </li>
</ul>
<div class="tab-content" id="regionCaseTabsContent">
  <div class="tab-pane fade show active" id="regionCaseA" role="tabpanel" aria-labelledby="regionCaseA-tab">
    Quarterly performance by Region in Case A
  </div>
  <div class="tab-pane fade" id="regionCaseB" role="tabpanel" aria-labelledby="regionCaseB-tab">
    Quarterly performance by Region in Case B
  </div>
</div>

End of section quarterly performance by Region

Final Words about Quarterly Results
## Yearly Results {.tabset}
This content pertains to Yearly Results
### By Product
Yearly performance by Products
### By Region
Yearly performance by Region
Final Words about Yearly Results

关键细节说明：

• nav nav-tabs：用来创建标签栏的样式
• data-bs-toggle="tab" 和 data-bs-target="#id"：关联标签按钮和对应的内容面板
• tab-content 和 tab-pane：存放每个标签的内容，active 类指定默认显示的标签

方法二：用bslib包实现自动多层嵌套（更简洁） #

如果你愿意改用bslib主题，它对嵌套标签页的支持更友好，不需要手动写HTML，直接给各级标题加.tabset类就能实现任意层级的嵌套。代码如下：

---
output:
  html_document:
    theme: 
      version: 5
      bootswatch: paper  # 保持你原来的主题风格
    highlight: tango
    number_sections: false
    toc: false
    toc_float: false
---
# Result Discussion {.tabset}
We will discuss results here
## Quarterly Results {.tabset}
This content pertains to Quarterly Results
### By Product {.tabset}
#### Case A
Quarterly performance by Products in Case A
#### Case B
Quarterly performance by Products in Case B
End of section quarterly performance by Products
### By Region {.tabset}
#### Case A
Quarterly performance by Region in Case A
#### Case B
Quarterly performance by Region in Case B
End of section quarterly performance by Region
Final Words about Quarterly Results
## Yearly Results {.tabset}
This content pertains to Yearly Results
### By Product
Yearly performance by Products
### By Region
Yearly performance by Region
Final Words about Yearly Results

关键细节说明：

• bslib基于Bootstrap 5，扩展了R Markdown的tabset功能，支持无限层级嵌套
• 只要给需要转成标签页的标题（比如### By Product）加上.tabset类，其下的子标题就会自动变成标签页
• 这种方法代码更简洁，后续维护也更方便

内容的提问来源于stack exchange，提问作者jroy