>   (defun treesit-toggle-named-thing ()
>     (interactive)
>     (setq-local treesit-sexp-type-regexp
>       (unless treesit-sexp-type-regexp #'treesit-node-named)))
>
> For the example above it toggles between moving to the
> first character of 'if' and moving to the opening brace.

Actually, it's better to toggle between the traditional behavior
and navigation by the 'sexp' thing:

  (defun treesit-toggle-sexp-mode ()
    (interactive)
    (setq-local treesit-sexp-type-regexp
                (unless treesit-sexp-type-regexp
                  (if (treesit-thing-defined-p 'sexp nil)
                      'sexp
                    #'treesit-node-named))
                forward-sexp-function
                (if (eq treesit-sexp-type-regexp 'sexp)
                    #'treesit-forward-sexp
                  #'treesit-forward-sexp-list)))

The only ts-mode where the 'sexp' thing is well defined is c-ts-mode with

  (sexp (not ,(rx (or "{" "}" "[" "]" "(" ")" ","))))

All other ts-modes contain desperate attempts to emulate the
traditional behavior to navigate symbols with the 'sexp' thing.
But symbol navigation is now implemented as the default behavior.

So these ts-modes should be fixed based on the pattern in c-ts-mode.
Then after toggling to the sexp mode they will navigate all ts nodes
except nodes that define boundaries.

Here is an example how such fix will look for ruby-ts-mode: