I am going though this right now and went back to your post on the grub2win forum with more details! I was hoping to find a more concise solution to my particular hardware.
I have a ThinkCentre m75q-1 little ryzen PC with a 3000g and I mostly want to play ps2, xbox, hopefully FZERO on GC I love that game and none of my emu systems can run it full speed all the time :/ Mudrunner PC, Phantasy Star Online etc
It uses an m.2 drive with w10 on it for primary and also a 1tb hard drive with hopefully Barocera and around 800gb reserved for Data for steam games and stuff on Windows. With a portion of the remainder of space on the secondary drive, the HDD, I want to install Batocera and have the SHARE folder accessible for obvious reasons, so I can be in either OS environment and be able to access the folder for easy tinkering
All that being said, I just want to dual boot into windows 10 with my current install and not lose anything and also boot into batocera whenever I want, but mostly for testing performance of the 3000g on Xemu and pcsx2 on Batocera. Help me out if yall want :) I am clueless on how to use grub2win, I tried enabling it and in Windows using CMD and it said success but was still windows boot loader and also using portable linux Mint and boot repair with no luck, it goes right back to windows even after it says it has selected Batocera in boot repair. Thank you I am sleepy so my sentences are bad haha