Recover Bootcamp EFI Folder/fix boot entries? I had macOS and Windows 10 installed through Bootcamp on my Macbook Pro (late 2013) and everything worked fine. Then I tried installing Ubuntu on an external drive and setting up pure-EFI triple boot. However, in the process I accidentally deleted the original EFI folder (not the partition, just the folder) and now the option for Windows doesn't show up when holding down ALT/Option key during startup, though I am able to boot into macOS and Ubuntu without problem. I noticed the EFI folder in /dev/disk0s1/ (the EFI partition) has only an APPLE folder but is missing the Microsoft one. I wonder if there is a way to recover the EFI files/entries and fix this problem so I can boot into Windows again?

If I remember correctly, I deleted the original EFI folder by doing this in Ubuntu:

$ sudo mkdir -p /mnt/sda1
$ sudo mount /dev/sda1 /mnt/sda1
$ sudo rm -r /mnt/sda1/EFI


Now when I boot into macOS, I can still see the BOOTCAMP partition with my Windows files on it. Also, System Preferences--&gt;Startup Disk still recognizes two System, the macOS and the "BOOTCAMP Windows". However, selecting the latter and reboot would lead to a black screen with error message reading "No bootable device found."

In macOS, typing diskutil list returns this:

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *251.0 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                 Apple_APFS Container disk1         164.0 GB   disk0s2
   3:       Microsoft Basic Data BOOTCAMP                86.3 GB    disk0s3
   4:           Windows Recovery                         471.9 MB   disk0s4

/dev/disk1 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +164.0 GB   disk1
                             Physical Store disk0s2
   1:                APFS Volume Macintosh HD            148.7 GB   disk1s1
   2:                APFS Volume Preboot                 20.7 MB    disk1s2
   3:                APFS Volume Recovery                506.6 MB   disk1s3
   4:                APFS Volume VM                      1.1 GB     disk1s4

/dev/disk2 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *256.1 GB   disk2
   1:                  Apple_HFS Ubuntu                  536.9 MB   disk2s1
   2:           Linux Filesystem                         131.1 GB   disk2s2
   3:                 Linux Swap                         17.1 GB    disk2s3
   4:       Microsoft Basic Data                         107.4 GB   disk2s4


Is there anything I could do to get back into my Windows system? Many thanks in advance.
I suppose you will need a Window 10 installer flash drive. If you do not have this flash drive, you will have to build one. First download the 64-bit Windows 10 iso from this Microsoft web site. This can be done while running macOS. Next you will need 16 GB or larger flash drive. For your model Mac, I believe the Boot Camp Assistant will aid in the creation of the Windows installer flash drive. If not, let me know.
If the root folder of the flash drive contains the file AutoUnattend.xml, you will need to rename the file to NoAutoUnattend.xml.
Boot to the flash drive. Hold down the option key at start up. From the Startup Manager, select the icon labeled "EFI Boot".
Open a Windows Command Prompt window, by following the procedure outlined in this step. Below is an image of what is initially displayed by the Windows 10 installer. Select "Next".



In the image shown below, select "Repair your computer".



In the image shown below, select "Troubleshoot".



In the image shown below, select "Command Prompt".



The result should be the image shown below.


Use the diskpart command to determine the drive letter for BOOTCAMP partition.

diskpart
list volume
exit

Enter the command below to assign drive letter S to the EFI partition.

mountvol S: /s

Here I will assume the BOOTCAMP partition is assign the drive letter C. Enter the command shown below to recreate the boot files.

bcdboot C:\windows /s S:

Enter the command shown below, then select option to "Turn off your PC".

exit