After going though significant problems and several retries I was finally able to install Windows 8.1 with full UEFI and get Secure Boot working without warnings on my new GA-Z87X-D3H based pc. Nice!

In that mode, it is normal that you cant access the BIOS by pressing DEL during startup. You have to do Change PC Settings, Update and Recovery, Recovery, Advanced Startup, Troubleshoot, Advanced Options, UEFI Firmware Settings, Reset.
Then it should boot into the firmware settings automatically.

My problem is that this does not work for me. It just reboots and comes back at the normal Windows 8.1 login prompt. I can't get into the UEFI settings and modify the settings anymore (of course, I could re-flash and start over with new settings, but that is not how it should work).

Am I doing something wrong? Did I miss something during installation? Or something in the bios not working correctly?