ATMA V works within windows 10 on the old save files.
I've been busy making mules and moving items over from my old save files onto them as well as cherished characters and copying them into the D2R save game folder.
One they are there and you've accessed the character in D2R game, you can't access them ever again with ATMA 5.
At this point in time, mules seems to be the only answer.