++todo
Change emit/capture mappings
Add s:set_marks_around_current_macro_characters
Small refactorings
Replace get(s:macro_characters, …) with s:macro_chars getter
Extract s:move_to_current_element_terminal()
Remove unneeded variable
Remove s:set_marks_around_current_macro_characters()

This does not seem useful
Handle leading macro chars in sexp#stackop