Paredit is perhaps the original structural editing tool. Its basic functionality of balancing parentheses is still essential to preserve the structure of the code, and Symex uses this functionality from Paredit even today.
Symex’s modal nature is its primary difference from Paredit. In addition, Symex’s core approach of employing a DSL on top of primitives allows you to describe specialized and custom tree-structured operations using a high-level DSL, so that you can implement your own paredit-like features without needing to know Emacs Lisp (for example, paste for a basic implementation of “emit forward” (aka “barf”).). The Symex DSL is easy to learn, and expresses computations in a very intuitive way.
Symex uses Paredit to balance parentheses in Lisp languages. If you’re prefer to use a different tool for this purpose, please See Balancing Parentheses.