I’ll never use an external monitor on Windows without this app

I had only used my laptop for work for the longest time, so a couple of years ago, when I switched to a multi-monitor setup for the first time, I faced a big surprise: Windows cannot control the brightness of external monitors. Yes, those little sliders you see in the Quick Settings panel and in the Settings app—the ones that make adjusting your laptop screen effortless—do absolutely nothing for an external display.