Using DiskPart you can unhide an EFI partition on a GPT volume:
select volume #
The default GPT ID for a
EFI System partition is
c12a7328-f81f-11d2-ba4b-00a0c93ec93b, converting to a
Basic data partition with the ID
...C7 automatically unhides the partition.
I have had success with this command prior, but I believe it was for MBR (msdos) partition table.
attributes volume clear hidden
Failure to change the partition type before clearing the hidden attribute, results in this diskpart error message:
Virtual Disk Service error:
The object is not found.
You most likely want to set the ID back to EFI when you are done (eg: modifying BCD)