If Windows cannot detect the second monitor after waking up from Sleep mode, then here some working solutions to help you fix the issue.

If your mouse cursor doesn't move to the second monitor in Windows 11/10, your displays might be aligned incorrectly. Use these fixes to resolve the issue.

Using a laptop as a monitor for another computer allows you to not only mirror your computer's screen on the laptop but also extend it, meaning you can show different content on both screens.