org-cycle-separator-lines

org-cycle-separator-lines is a variable defined in `org.el'.
Its value is

2

• This variable is safe as a file local variable if its value
  satisfies the predicate `integerp'.

Documentation:
Number of empty lines needed to keep an empty line between collapsed trees.
If you leave an empty line between the end of a subtree and the following
headline, this empty line is hidden when the subtree is folded.
Org-mode will leave (exactly) one empty line visible if the number of
empty lines is equal or larger to the number given in this variable.
So the default 2 means at least 2 empty lines after the end of a subtree
are needed to produce free space between a collapsed subtree and the
following headline.

If the number is negative, and the number of empty lines is at least -N,
all empty lines are shown.

Special case: when 0, never leave empty lines in collapsed view.

You can customize this variable.