I think I figured it out, I managed to disable CSM by default and enable 4g decoding on default through AMIBCP 4.55 for an X79 motherboard - which should be a similar idea to Z87.
The reason why it doesn’t work sometimes is because simply there are more than one instance of the setting enabled or disabled, so all of them need to be set to default and failsafe for it to work - Usermode for all menus and submenus that contain it seems to help it show up, too.
so in your Z87 there is no string for above 4g and csm toggle, but could you manage how to find/enable the above 4G and force it to CSM Off if there is no such option through amibcp?
Please read above, X79 is the motherboard that I managed to verify it on, an Asrock X79 Extreme 6 Motherboard
Also got it working for all of 1 reboot on windows 11 with a 9980HK on a Maximus VIII Hero. I remember reading about deleting a DXE to make space for the driver – or perhaps put it at the front of the DXE stack?
I’m working on the Z87 bios tonight
Interesting, I can find “Above 4G Decoding” string to token ‘0x0F97’ in the bios file with AMIBCP v4.53.
But it is unable to find this string in the “Setup Configuation”, it’s even not a hidden option.
this is ASUS B85-Plus 2305 bios inserted with “NvmExpressDxe_5.ffs” and “ReBarDxe.ffs”, but when i’m trying to patch the DSDT follow the wikis, it is totally different, there is no CreateQWordField in my “DSDT.dsl”, is there anybody interested in it or you can help with it? thanks 
B85PLUSNVME_Bar.rar (6.5 MB)
Check everywhere, but Asus probably never even inserted it into the bios in the first place 
Got this now, the bios with the DXE installed and the CSM modes disabled? I think I pretty much covered all CSM mode settings.
https://drive.google.com/drive/folders/1qlKZ_LwmIetdKAjuCCY9eL3hB1QvtiSI?usp=share_link
Keep us updated, and thanks for helping hack it in 
One more thing, is there any way to inject TPM 2.0 compatibility instead of 1.2 only? I have some files dug out from an X99 Bios from Gigabyte’s SLI motherboard, which has TPM 2 code, but not sure if you can just drag and drop the corresponding 4 or so files – or if there’s anything else needed
@Wingklip I’m also interested in the TPM 2.0 mod so I can upgrade to Windows 11 and be able to play Valorant (requires TPM 2.0 on 11).
I wrote some of my findings here [Discussion] TPM 2.0 on unsupported motherboards
It requires DSDT modification in addition to DXE (especially the TPM SMI handler) and maybe PEI modules swap/add
