how can I add a second monitor without being detected in multiple display check?

Just you can mirror...first decide what you want....

setting > display > display section and click detect

I think the 2nd monitor

you have to choose the main one from setting make it main and the problem is solved and if it doesnt work try to use hdmi cable

If you want to add a second monitor without it being detected in the multiple display check, you can try the following steps:

1. Connect the second monitor to your computer's graphics card or integrated graphics port.

2. Press the Windows key + P to open the "Project" menu.

3. Select the "PC screen only" option. This will disable the second monitor without removing the physical connection.

4. Adjust the display settings to make the second monitor "Disconnected" or "Not active." You can do this by right-clicking on the desktop, selecting "Display settings," and then identifying the second monitor. From there, you should be able to disable or disconnect the monitor.

By following these steps, the second monitor will remain physically connected to your computer but won't be detected or used in the multiple display setup. Keep in mind that depending on your graphics card and drivers, the steps to disconnect the monitor may vary slightly.