You can dual-boot any number of Windows on a W10 UEFI PC if they're Vista, W7 W8 W8,1 or other W10 OSs
You can't boot any legacy Windows from DOS through to XP, or any "foreign" OS like Linux.
All the things allowed in the MBR/BIOS version of MS bootmgr were removed from the bootmgr.efi version, and there's nothing that EasyBCD (or anyone else) can do to circumvent the prohibition.
Follow the advice in the link Peter gave for you best option, allowing Linux (if that's what youre trying to dual-boot) to take control of the boot then use grub to dual-boot W10