Managing hard drive partitions might seem intimidating, but it’s a straightforward process with the right tools. Windows ...

I'd try doing a diskpart on that drive and issuing a 'clean' command to wipe away the current partition. The fact that there's a single partition that's covering the whole disk might be the problem; ...

No idea why the SSD isn't listed as a boot option. The only thing I can think of is that the BCD on the 4TB drive isn't configured properly, or the boot files didn't get copied properly to the EFI ...