This package provides a text object for Evil for working with symexes. It also prevents normal Evil commands like dd (delete line) from breaking parenthesis structure. If you are an Evil user, this would be a good way to edit Lisp code that augments the familiar Evil compositional style.
Symex is harmonious with Evil but totally separate from it, as it is a distinct mode. While Evil-Cleverparens makes Normal state behave better with respect to structure, Symex is oriented directly around structure, offering a large array of structural features. Due to this different emphasis, if you are an Evil user, you may prefer to use Evil Cleverparens together with Symex, to simultaneously gain advanced tree-structured editing while also enhancing Normal state to be structure-aware.