You can add in your header
navigation: horizontal # or vertical or frame
Like this
---
title: 'Title'
author: 'Author'
date: February 02, 2022
output:
beamer_presentation: default
fontsize: 12pt
navigation: horizontal
---
## Section
Stuff
Documented directly in Pandoc documentation: Pandoc - Pandoc User’s Guide
This should work as expected.