I’ve somehow managed to mod the bios and unlock the Advanced menu. Credit goes to @Lost_N_BIOS. Thanks!
All I had to do was extract this section "Section_PE32_image_DriverSampleDxe_SetupUtility_body.efi’ using the UEFITool and edit with a hex editor like this:
Then using the UEFITool again (version 0.21.5) I replaced the original with the modded one and then saved the .bin file.
To flash it I used the fptw64.exe tool, and in this part I was trembling with fear of bricking my one and only computer, but thankfully everything went ok. Cheers!