You might find this helpful. It's a slightly reworked super_edits file that allows you to split individual lines on an order. So for example if a customer orders 5 widgets and you've only got 3 in stock, you can move 2 to another order using super_edit's edit orders function without having to do all that deleting orders and using "encrypted password" to reconstruct them from scratch.
It's not the most elegant of code and you will still need to tweak the tax and shipping figures by hand, but it's a lot more straightforward (and less work) than the alternatives.
super_edit.zip
Bookmarks