Windows boot option missing after installing redhat/ centos in dualboot

Check that windows is detected. Run following command:

grub2-mkconfig

If Windows was listed anywhere, lets save the new configuration file by first making a backup first, just in case.

backup:

sudo cp /boot/grub2/grub.cfg /boot/grub2/grub.cfg.old

save the config file:

sudo grub2-mkconfig -o /boot/grub2/grub.cfg   

Reboot your system, now you must see Windows option in boot menu.