I only play by myself and thought it would be nice to constantly have my game saved but I absolutely hate the fact that the map resets everytime.
Can’t exactly do what you’re asking since bnet characters are stored server side.
What you can do is make a D2 (original) character, edit it with a hero editor and export it to your offline character save folder since those are stored on your computer, rather than blizzards servers.
It’s also possible there’s an offline character editor mod for d2r where you could just spawn items into your offline game and level up your character with commands or something. But I haven’t kept up to date with mods so this may be a fictional thing.
The first one 100% works I’m sure of though