Please try to help the OP to fix his dual boot problem.
As far as I know mixing macOS in UEFI and Windows in Legacy mode and running the 2 systems from a single hard disk from 2 separate partitions is not an easy task for most, especially those who have not done a lot of dual booting.
If you have an illustrated guide showing your special steps, please post that to help OP.
I have several computers I have built with different motherboards , CPUs and Graphics running triple boot setup running very well from separate hard disks. I have my own reasons to use separate hard disks for different Operating Systems. I also believe for newcomers to multi-boot that is much easier to set up and run.
I also know how to set up and run dual boot from separate partitions from a single disk using both systems using either legacy mode or UEFI mode. But, as I said, I prefer multi-disk multi-boot systems and I don't try to mix UEFI and Legacy boot from a Single disk because they are problem prone.
The steps needed to accomplish Single disk Dual boot Windows 10 and Mac OS system in UEFI mode that I use are as follows and the method works flawlessly for me.
- Create a macOS Sierra installer USB Flash disk using Tonymac Unibeast method.
- Take that Sierra USB Installer disk to the Computer (with OS X /MacOS compatible hardware) you want to create a Single disk separate Partitions Hackintosh_windows 10 Dual boot System.
- Disconnect all the hard disks from that Computer connecting only a Single SATA HDD or SATA SSD or NVMe disk as the target for installing the 2 systems. This is to avoid a lot of confusion in Disk utility screen with too many disks with similar sounding brand names. Remember NVMe needs additional steps so not a good idea for the beginners.
- Remove all the USB devices except Keyboard, Mouse and the Sierra USB installer, again for simplicity.
- Boot with the Sierra USB installer connected to a proven working USB port.
- Press the Hotkey(like Del) to enter the BIOS setup for the MoBo.
- MAKE SURE YEAR/MONTH/DATE/TIME are current
- Make the Sierra USB installer as the first boot device in Boot Options Priorities.
- Make all other REQUIRED choices in other BIOS setup options for successful macOS booting as recommended in the Guide or other successful installations found in the Forum for your unusual hardware.
- Boot the Sierra USB Installer to Installation screen >Disk Utility and locate your Single target Disk.
- Create 2 Partitions in the disk
- Make Partition 1 as "Sierra System" with GUID /MacOS Extended (Journaled) Partition scheme and Format respectively.
- Format the remaining unused partition also as macOS Extended (Journaled) for now*** (see Step #44) but rename it as "Windows 10"
- Exit the Disk Utility and go to MacOS Installation screen
- Click on the Partition named "Sierra System" and also choose the Essential files and start the installation.
- Carefully follow the steps to reboot the Sierra System disk to complete the installation
- Once all system files are fully copied to the Sierra System disk (may take 30 -40 minutes in a 2-3 reboots) and you complete the Setup including the iCloud ,Keyboard, current date and time etc, run Multibeast 9.1.0 to install UEFI boot Mode+kexts ( Audio/Ethernet/ USB/) + Graphics configuration in some cases + System Definitions+ and any special patches for NVMe using other methods.
- Reboot still accessing Boot menu through hotkey >Sierra USB installer>CBM > Sierra System Disk >Login Screen>Desktop
- Download and launch Clover Configurator Vibrant edition.
- Click on "Install/Update Clover" menu from the Left Panel of CCV screen
- Click "Check Now" button on the Right bottom of that screen to see the current booted version of Clover EFI bootloader ( which will be that of Multibeats 9.1.0)
- Remote Available Version will be the most current which you need to select and update the Sierra System Disk Clover EFI bootloader.
- Choose the Sierra System Disk and make Sure UEFI mode is once again chosen and in drivers64UEFI OsxAptioFix2Drv is also checked before installing Clover EFI on the System Disk to update it to the current.
- Once Clover EFI Installation is completed with the updated version, open EFI>EFI>CLOVER > kexts>Other and copy and paste FakeSMC + Ethernet kext and any other kexts like RehabMan's GenericUSBXHCI.kext or RehabMan's "Fake PCIID kexts " on a need to use basis for the hardware used.
- Edit config.plist in CCV making sure to check all menu there and include needed selections and remove unwanted ones especially from ACPI and Boot Args: [ I can be only very general here as hardware Specs for each system determine the Specifics in this editing]
- Reboot and go to BIOS Setup and make the UEFI SATA HDD/SSD or NVMe as the first boot device
- DISABLE other disks from the Boot Option priorities
- In CBM screen, go to Options> Boot Args:- and all sub menus to make sure they are appropriate for booting
- Boot the Sierra System Disk
- Login to desktop
- Launch Terminal : sudo spctl --assess --master-disable> Password .
- Make sure correct Date and Time is set using password
- Check Apple>About This Mac> Overview
- Check System Report..>Hardware and all the submenu to confirm all kexts are properly loaded
- Open System Preferences to configure "Sound", "Network" "Energy Saver" etc etc.
- Go to "Apple Store" and look for updates and Install as needed
- Reboot and check for flawless booting without the USB installer
- Run Terminal and "diskutil list" command
- Note the Partition that was set aside for Windows 10 but still in HFS+ file system . Specifically check its size. Its unused size will be larger and a clue to select the right partition to Install Windows 10.
- Now boot with Windows 10 USB installer created using Rufus in GPT/NTFS
- Press Hotkey to go to Boot Menu to select the Windows 10 USB installer disk to boot from.
- Go to New Installation option.
- From the listed disk partitions select the disk noted from Diskutil list command as Windows 10.
- Click ***Delete to delete that previously HFS+ formatted partition set aside for Windows 10.
- New unused (empty) partition will be displayed along with other 3 partitions on the Sierra disk
- Select that Unused Partition to start Installing Windows 10
- Windows 10 will be installed in UEFI mode and NTFS filse sytem in that partition
- You keep on booting that partition on prompt until full installation and updates are completed.
- Then you press the appropriate key to enter the BIOS setup and choose the Disk in UEFI as first boot and disable everything else in Boot Option Priorities.
- Clover EFI boot loader will mount both System disks in CBM screen and you can choose either macOS or Windows 10.