It seems there are plenty of posts out there but most involve separate OS's on a single drive, and many involve BIOS.

I have two separate installations on separate SSDs. All are using UEFI.

I have a Windows installation on ssdOne. I disconnected ssdOne and installed latest Fedora on ssdTwo. I rebooted and installation appeared to work, so I reconnected ssdOne and tried booting into Windows. Windows boots and I call it a night.

Now today I want to get into Fedora. Holding F12 on startup I'm posed with two options
1. Windows Boot Manager
2. Fedora

I choose 1 and it boots to Windows as it should, but if I choose 2, it boots to Windows.

I'm sure everything is intact as I haven't made any alterations since installing, but I'm not sure how to get Fedora to boot. Please help.

When you disconnected ssdOne and installed Fedora, the Grub bootloader was installed on SSDTwo. Reconnecting SSDOne means that the system will always try and boot from SSDOne which is Windows... Every time a coconut!

Had you just installed Fedora on SSDTwo with everything connected it would have installed Grub on SSDOne and Grub would give you the choice of Windows and Fedora which would work.

As I know little about UEFI as I haven't had to tangle with it as yet, I'll let someone else with more knowledge explain how to fix your problem. (Probably by installing Grub on SSDOne?)

Play Bonny!

With MBR firware, a case can be made for removing the Windows device before installing Linux. I've done it myself.
No such case can (probably) be made with UEFI firmware. The (initial) boot selection menu is in NVRAM, not in the bootloader - there is a UEFI shell environment that enables you to update the NVRAM. Don't even think about it.
Connect both SSDs and reinstall Fedora to the second SSD. It will use the efi partition Windows created (in normal installs) - I doubt it will recognise the efi partition on SSD2, but it might be worth checking the mount for /boot/efi during the install.
If you find two "Fedora" entries after all this, you can use efibootmgr to remove the defunct one - carefully.

I had a feeling this was the case. Was hoping I wouldn't have to reinstall. So I guess my only remaining question is if I have to have an EFI partition on the SSD2. Or, can I point the installer to the existing EFI partition on SSD1 and only have a root partition and a boot partition on SSD2?

Actually now that I think of it I'm pretty sure I have to have an EFI partition on both, regardless. I don't believe the installer allows you to choose one from another drive. So I guess I don't have any more questions.

Thanks for the help.

A couple of options

Boot grub

Go to setup and set the second drive as the boot device. Boot into Linux and setup grub to boot windows from there.

Boot windows 8

Boot into windows and configure the windows loader to boot Linux

With this boot loader it loads windows 8 first but does not show the login screen. Should not take too long with ssd.

The Fedora install would have created an efi on the drive - with both SSDs in it is superfluous. Only one is ever needed.
You need to ignore that - you have to ensure the Fedora installer is using the Windows one; check at the partitioning stage for the /boot/efi mount.

Moved: This thread is more suitable in <Fedora> and has been moved accordingly to help your thread/question get the exposure it deserves.

I reinstalled Fedora without disconnecting the Windows drive. I installed same as before, but installer obviously did its own thing in terms of installing whatever is necessary for it to boot properly. Everything is working so far. The login screen is incredibly laggy, but at least this particular issue is solved.