- can show as special arg any dynamically scoped vars when they are used (not passed) in that function.

- on ~Node(), must check that selected.n is not equal.. maybe also focus, copybuf etc

- double check: it is now possible for PHs and args to not match..
- double check: it is now possible for a PH to be the root of a function

future refactorings:
- after refactorings the LCA can be moved lower in the tree for some placeholders
  if a function is used once and has 1 PH, and its LCA is lower than the root of
  the function, the function can be moved down.
