Is there a tool to .....

Just view items on all my characters? I would kill for that, no stash changer, no changes to game : just an overview of the items (with viewable stats) i got on all my characters and their stashes.

Does it exist?

Not that I’m aware of. Just use one of the stash managers. They literally do the same exact thing and make NO changes to your game unless you specifically tell it to do so.

Just fire one up and easily view and navigate between all your characters. Can’t say I understand some people’s irrational fear of using a tool that allows you to “cheat” but in no way forces you to do so. They have more uses than just cheating, one of those uses is what you want, to simply view your stuff. They do that.