i stumbled upon this question but answer did not fit for me
so i googled more and posting here answer which worked:
https://www.onetransistor.eu/2014/09/make-bootable-windows-usb-from-ubuntu.html
there are four options covered in the link, i'll describe here one suitable
install GParted
select inserted flash drive
unmount
Device -> Create Partition Table -> msdos -> Apply
right click the unallocated space -> New
make a primary NTFS partition and give it a label
Apply all operations
right click the partition -> Manage flags
select boot
copy files from windows.iso
sync (takes a lot of time, if you want to see progress find how here on stackoverflow)
install grub-pc-bin
sudo grub-install --target=i386-pc --boot-directory="/media/<username>/<drive_label>/boot" /dev/sdX (also takes some time)
touch on usb /boot/grub/grub.cfg and copy there:
default=1
timeout=15
color_normal=light-cyan/dark-gray
menu_color_normal=black/light-cyan
menu_color_highlight=white/black
menuentry "Start Windows Installation" {
insmod ntfs
insmod search_label
search --no-floppy --set=root --label <USB_drive_label> --hint hd0,msdos1
ntldr /bootmgr
boot
}
menuentry "Boot from the first hard drive" {
insmod ntfs
insmod chain
insmod part_msdos
insmod part_gpt
set root=(hd1)
chainloader +1
boot
}
don't forget to replace anything <...> with your data
after that i got bootable flash with windows install