Insert query with a subquery
If the (subquery) has SELECT (whatever expression) AS col FROM ..., then you can do:

INSERT INTO mytable 
  (col1, col2, col3, col4) 
SELECT 
  val1, s.col, val2, val3
FROM 
  (subquery) AS s ;


or:

WITH s (col) AS
  (subquery)
INSERT INTO mytable 
  (col1, col2, col3, col4) 
SELECT 
  val1, s.col, val2, val3
FROM 
  s ;