I think it would be a good idea for a "How to Mini Guide" section where people can go for instant information on how to rectify various computer problems. for example here is one i made below: moderators please feel free to sticky.

Step by step 100MB bootable EFI partition restore procedure:

When an EFI partition is deleted, you can make your single/multi-boot Windows10 operating system bootable again by recreating a new one by using the Command Prompt. Skip step 1 if your second/other Windows10 operating system is bootable and functioning.

1. Boot your computer using the Windows 10 installation media or Windows 10 recovery disk. On the first screen, press SHIFT+F10 to enter the Command Prompt.

2. Run the commands below to shrink a partition for unallocated space:

diskpart

list disk

select disk # ( Select the disk where you want to add the EFI system partition)

list partition

select partition # (Select the main operating system partition which you want to shrink)

shrink desired=100 (Shrink the selected partition by 100MB.)

3. Run the following commands to create the EFI system partition with the unallocated space:

create partition efi size=100

format quick fs=fat32

assign letter=Z (You may replace “Z” with any other unused drive letter)

exit

4. Use the command below to copy the boot files from the currently running windows partition to the newly created EFI system partition and create the bootable BCD store in it:

bcdboot C:\windows /s Z: (“C” is the drive letter of the system partition and “Z” is the drive letter you want to assign to the newly created EFI partition.)

exit

5. Restart your computer then enter the UEFI to select a primary windows bootloader