Yes, you can.

If you have an E5 (or any 10* and above) and you wish to change it to something else.

You can go to Enabling page and you will have 2 options. Replacement or Regression.

So for example, if you want to replace Hero A (E5) to B, you would need 9 copies of hero B. All you lost would be the 9 copies of hero A. For 10*, it would be 5 copies, etc.

If you regress it, you'll have the same exact ingredient in puppets. For E5, it'll broken down to 9 copies of hero A, 3x 10* puppets and 3x9* and the 6*s and 5*s (can't remember exactly how many). While you did not lose the hero copies, you lose all the cash and spirit spent on Hero A.

So depending on which sacrifice you're willing to made. And you also need 5 soul symbol that you can get by using 300 scrolls in a scroll event.