I have been working on this new history editing tool since the old scenario editor is no longer being supported for recent expansions. It currently edits only province history, but it has been very useful to me for both visualizing and tweaking my mods. (I also found a lot of bugs in vanilla!). It's a relatively new tool and it probably has bugs, so before I release it and ruin someone's life, I want to do some testing and iron it out a bit.
Here are some screenshots:
Here's the link:
EU3 History Editor
PS. This is only compatible with DW. If you load another version of the game, it will probably work for the most part, but you will lose information when you save. If there is any demand, I can add some compatibility.