Chapter 14 Search this book
From the bookdown book:
The second button on the toolbar is the search button. Its keyboard shortcut is F (Find). When the button is clicked, you will see a search box at the top of the sidebar. As you type in the box, the TOC will be filtered to display the sections that match the search keyword. Now you can use the arrow keys Up/Down to highlight the next keyword on the current page. When you click the search button again (or hit F outside the search box), the search keyword will be emptied and the search box will be hidden.
For the Up/Down arrow navigation to work, remember to leave the cursor in the search box. To move to the next file, select it in the sidebar, then return the cursor to the search box and use Up/Down.