Sure, but Lunar does not actually turn off the macbook display, only mirrors the external display to the macbook display (so you don't have two desktops) and sets its brightness to 0%.

If your goal is to conserve battery life, you can turn the brightness to 0% any time using the brightness slider.

I don't think a similar feature will make into MonitorControl as this is outside of the scope of the app (the consensus among maintainers is that the app is already a bit bloated if measured against the original vision/scope, there should be a simplification in the future instead so the app will be easier to maintain and more maintainers can join in), but will add it to BetterDisplay eventually.

Ah okay, sure; I'll just stick to 0% brightness then. Thanks!