I had trouble with this issue too, but eventually I figured it out. The command line works very well, if you are not too imtimidated by it.
You need to determine the placement of your target (windows, in your case), at the grub bootloader menu list. But you need to start counting at zero. So, if windows is 3rd from the top, it would be number 2 (this is unix convention of counting).
Then you need to edit grub, which is in the subdirectory default, which is in the etc directory.
If you know how to gain "root access" (superuser) at a terminal, type and enter:
Change the line that says:
Then save and exit
Then type and enter:
grub2-mkconfig -o /boot/grub/grub.cfg
Now you can reboot to see if you were successful.
Remember, you must be at a root terminal for this procedure to work.