Hi there
Same problem here, and you are right, I think it was 2012 last one that work for me with saved own styles.
None of these own styles won't be seen with style picker so I stopped making them
These days I have folder OwnStyleSongs saved there sgu or mgu file with my own style (I use _BLANK midi styles start with, 4 different I think there is) add one by one or only one instrument (RealStyle) to this, then open it and start from there, don't use NEW command, it will destroy all what you made up, just delete if you have chords / melody there.
I have heard rumors about .LS3 files but can't use them or .LS3 won't work
So if there is anybody who can use these .LS3 files please copy and paste here part of it please (if it works for you)
Thanks
Isse / Finland