In case of any OS installation, you need to make a backup beforehand anyway. So just backup everything you need to a different hard drive, that won’t be present during installation. Then install Windows. Override the Windows Bootloader with GRUB2. If you have 2 hard drives within your computer, it is even easier. Install Linux to the first one, Windows to the second one and all you have to do after all is to change the boot order within your UEFI for the Linux HDD to be first in the chain.
Make sure you create a separate partition for Windows and then install Windows only to this partition.