您可以使用\addcontentsline 执行此操作。
---
title: "Untitled"
output: pdf_document
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```
## R Markdown
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Sit amet cursus sit amet dictum sit amet justo donec. Donec massa sapien faucibus et molestie. Varius quam quisque id
\addcontentsline{toc}{section}{plot one}
```{r cars}
plot(mtcars$mpg)
```
## Including Plots
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Sit amet cursus sit amet dictum sit amet justo donec. Donec massa sapien faucibus et molestie. Varius quam quisque id
\addcontentsline{toc}{section}{plot two}
```{r pressure, echo=FALSE}
plot(pressure)
```