If you have an existing Windows 7 / Linux Mint dual boot system, a simple upgrade to Windows 10 didn't disturb the Linux install or the dual boot. This was on a MBR partitioned system. I had an existing Windows 7 / Linux Mint dual boot on a Dell Inspiron 1545 laptop and upgraded to Windows 10. The dual boot and the Linux Mint were not disturbed by the Windows 10 upgrade. But you offer good advice for adding Linux Mint to an existing Windows 10 install. That worked great on another system that I have that also has a UEFI/GPT partition.