This configuration variable is one of two variables that affect the appearance
of character-based Tree-View controls. TREE_TAB_SIZE controls the number of screen columns between each level in the visual
representation of the tree. For example, if TREE_TAB_SIZE is set to 10, the horizontal distance between the first character of text
in the first level and the first character of text in the succeeding levels of
the tree will be 10 screen columns each. The default value of TREE_TAB_SIZE is 3.
See TREE_ROOT_SPACE variable.