Disclaimer~ I am not responsible for what you choose to do to your devices. With that being said I have years of overclocking experience under my belt and feel comfortable enough to try this out on my own steam deck. All of my desktop monitors have a stable overclock to them and when i saw i could possibly do the same to my Steam Deck i was super excited! I love experimenting with the Steam Deck to inch out every bit of performance available and with my pervious cooling mods i have no worries of the screen or any components of my steam deck overheating in the process.

tldw~
In Konsole enter sudo steamosreadonly disable
(enter sudo password)
Navigate to rootfs/bin then open file called "gamescopesession"
Scroll down to the line STEAM_DISPLAY_REFRESH_LIMITS=40,60
And adjust the 60 in that line to the desired Framerate limit
SAVE your changes (enter sudo password again)
Back in Konsole enter sudo steamosreadonly enable