Smart Key - Delimited Things ​

bash
In a programming or markup language buffer, when pressed/clicked at
the start or end of a delimited thing (including lists, comments,
strings, arrays/vectors, sets, functions and markup pair tags in a
markup language), and not at the end of a line:
  ACTION KEY
     Marks the thing for editing.
  ASSIST KEY
     Marks and kills the thing for yanking elsewhere.
Note that the press must be on the first character of the delimiter of
the thing.