However, if you choose to install EnOS first, you would need to do a couple of things to be able to install Windows later:
When you are done with the installation of EnOS, before you reboot the system, launch Gparted and shrink/resize the system partition to your desired size.
Then remove the boot,esp flag from EnOS’ ESP (EFI System Partition).
Next when you want to install Windows later on, you could just point its installer to that unallocated space that you freed up earlier. In this way Windows would create its own ESP and won’t be touching your EnOS install.
Or, go with the most recommended way, install Windows first. Set it up and use its Disk Manager to shrink its system partition. Turn off Fast Startup and hibernation (if enabled).
Install EnOS onto that unallocated space.
In case of any doubts, post your questions on the forum.
As mentioned above, this looks like MBR/BIOS/Legacy install.
Can you boot up Windows with this setup?
If positive, and since it looks like you have installed EnOS first and Windows later, the latter must have overwritten the MBR of the disk and consequently EnOS’ bootloader.
I was under the impression that you were able to boot up your Live USB in UEFI mode after disabling CSM/Legacy boot mode in BIOS.