If reinstalling macOS over top of itself does not recreate the hidden EFI partition, then you will most likely need to perform a clean install of macOS by first erasing the whole physical drive followed by reinstalling macOS & restoring from backup. Then using Bootcamp Assistant to install Windows.
You can actually create an ESP (aka EFI) partition, but I'm not sure how to do that from either macOS or a Windows installer. It also does not help that macOS does not like to create super small partitions these days. The EFI partition actually needs to be "tagged" as an ESP partition. Technically that partition can be located anywhere on the drive, but it is traditionally placed as the first partition so it is out of the way if partitions need to be resized/modified.
I did find this post online for creating the ESP partition using the Windows installer.
https://superuser.com/a/1308330
You will need to use the Windows installer to delete the current Bootcamp partition so that you can create the ESP partition (you will need to figure out how to delete the current Bootcamp partition using the Windows installer since it is not mentioned in those instructions....possible to do so from the command line or from one of the early steps in the GUI interface of the Windows installer). Then you can let the Windows installer utilize the remaining free space for the Windows installation (the installer will automatically configure the remaining free space properly for Windows). Keep in mind I have no idea if this will mess things up with BootCamp in any way since I have not attempted to use Bootcamp in decades.
Make sure you have a good backup of your macOS data before you try to do anything since all of these options are very risky to your existing data residing within macOS. If something goes wrong, then you will likely need to perform a clean in stall of macOS. I highly recommend having a bootable macOS USB installer handy so you have access to more options if reinstalling macOS becomes necessary, but if you have a 2018-2020 Intel Mac, then a bootable USB installer won't work unless you have modified the computer's security settings to allow booting from external drives. While most Macs have access to Recovery Mode/Internet Recovery Mode, many people find they have issues with it, plus some older "Obsolete" and possibly "Vintage" Macs may no longer be able to reinstall macOS through recovery mode since it seems Apple may have turned off the online macOS install servers.
