Excuse me, how does ASUS set SSD as the startup disk?

You can refer to the following steps:

1. Press F2 to Enter the BIOS, select the security boot menu in the security tab, press Enter to disable, and press F 10 to save;

2. After the computer restarts, click F2 to enter the BIOS, select Launch CSM in the boot tab, press Enter to select Enable, and press F 10 to save;

3. Press esc to select the startup item of the restart point and select the corresponding startup mode.