如何在Rmarkdown转HTML时为编号列表下的标题添加缩进？

问题分析 #

Markdown标题属于块级元素，会自动打断编号列表的上下文，导致你写的三级标题无法被识别为列表项3的子元素，手动添加空格无效正是因为这个特性——常规Markdown标题无法直接嵌套在列表结构中。

解决方案 #

方案一：使用HTML列表结构强制嵌套（最可靠）

直接用HTML的有序列表标签包裹内容，将需要缩进的标题和tabs模块都放在对应的<li>元素内部，这样能严格保持层级关系：

---
title: "Indent heading under list"
output: html_document
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)

This is a heading #

1. I have some numbered list items under this heading
2. And I want to have sub-heading under this numbered listed
3. Under this new sub-heading, I want to have tabs under it

   Sub-heading I want

   Apple

   • This is an apple

   Orange

   • This is an orange
4. I want the above sub-heading to have indentation so that it is indented under item number 3 above

方案二：借助Pandoc扩展的纯Markdown写法

如果你偏好纯Markdown语法，可以启用Pandoc的fenced_divs扩展，用块容器将标题和tabs包裹在列表项内：

---
title: "Indent heading under list"
output: 
  html_document:
    pandoc_args: ["--from=gfm+fenced_divs"]
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)

This is a heading #

1. I have some numbered list items under this heading

2. And I want to have sub-heading under this numbered listed

3. Under this new sub-heading, I want to have tabs under it
   :::

   Sub-heading I want {.tabset .tabset-fade .tabset-pills} #

   Apple

   • This is an apple

   Orange

   • This is an orange
     :::

4. I want the above sub-heading to have indentation so that it is indented under item number 3 above

### 效果说明
两种方案都能让三级标题缩进至列表项3下方，同时保留`tabset`的标签页功能。HTML方案兼容性更好，无需额外配置扩展；纯Markdown方案需要启用Pandoc扩展，但写法更贴近常规Markdown习惯。

内容的提问来源于stack exchange，提问作者benson23