I have Windows 8.1 installed on an SSD in my PC. It is my main OS and I use it the most. I currently need Linux for development purposes and I installed Linux Mint on the same SSD where Windows is installed. I want to have a USB flash drive, which, when plugged in, will show the GRUB bootloader and let me boot into Linux. Otherwise the PC should boot straight into Windows. When I was installing Linux Mint, I selected the USB flash drive as a "device for bootloader installation" but it seems that nothing was installed on the flash drive but I now have an "ubuntu" option in my UEFI BIOS boot devices list, which just launches Linux from its main partition and does this in Legacy BIOS mode, even though I installed Mint in UEFI mode. Also, I think that nVidia graphics drivers don't work because of the Legacy mode.
Can anyone provide me a complete, step-by-step noob tutorial on how to make a UEFI and Secure Boot compatible flash drive and install GRUB2 EFI on it, so it will let me boot into Linux Mint installation straight from the flash drive?