Now when I boot into macOS, I can still see the BOOTCAMP partition with my Windows files on it. If I remember correctly, I deleted the original EFI folder by doing this in Ubuntu: $ sudo mkdir -p /mnt/sda1 I wonder if there is a way to recover the EFI files/entries and fix this problem so I can boot into Windows again?
I noticed the EFI folder in /dev/disk0s1/ (the EFI partition) has only an APPLE folder but is missing the Microsoft one. 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.
Then I tried installing Ubuntu on an external drive and setting up pure-EFI triple boot. I had macOS and Windows 10 installed through Bootcamp on my Macbook Pro (late 2013) and everything worked fine.
