This app was mentioned in 6 comments, with an average of 1.00 upvote
Then I would suggest This app (not promoting Dev or anything) since it adds a tile to quick settings, pres it and it should keep the screen awake while it's active. If you don't like that one, search for any similar app, there are tons similar.
I use Keep Awake - Quick Settings Tile for the same thing, however it doesn't require Tiles. Just noting it as another option since I also have Tiles installed.
I use this app to keep my screen on. You install then it, then edit the quick settings by clicking the pencil. Then drag the new widget where you want it... https://play.google.com/store/apps/details?id=com.fchauveau.keepAwake
Works on my Android 10 (OnePlus 6)
https://play.google.com/store/apps/details?id=com.fchauveau.keepAwake