Boot into Windows 11 from the boot manager
Open Command Prompt as Admin and backup the BCD.
bcdedit /export C:\BCD_Backup
Now rebuild BCD:
bootrec /fixmbr
bootrec /fixboot
bootrec /scanos
bootrec /rebuildbcd
Open Windows 11 from the boot manager.
Open Command Prompt as Admin and list boot entries:
bcdedit /enum
Look for the entry that corresponds to your Windows 10 installation. Note the identifier (usually in the form of {xxxx-xxxx-xxxx-xxxx}).
Type the following command, replacing {identifier} with the actual identifier of the Windows 10 entry:
bcdedit /default {identifier}
bcdedit /timeout 5
Restart your laptop to see if Windows 10 boots by default.