Keep Awake
A long install, a demo, a call on the second monitor, a script you are watching finish — the times a screen lock is not a security control but an interruption. Leave this tab open and the screen stays on.
How it works. The browser's Screen Wake Lock — the same thing a video call or a map uses. It holds the display on while this tab is visible, and nothing more: it cannot stop the machine sleeping when the lid closes, and it does not touch any setting on your computer. Switch it off, close the tab, or move to another window for long enough and it is released.
It comes back on its own. Switching to another tab releases the lock — that is how the browser works, not a fault here. Coming back re-takes it, so a long job does not need watching.
Worth saying, given what we do for a living: a screen lock is a security control. This suspends it for as long as the tab is open, on a machine that is presumably in front of you. If you walk away, lock the screen yourself — this tool will not do it for you, and an unlocked machine in a client's office is a finding.