antlr-action-visibility

antlr-action-visibility is a variable defined in `antlr-mode.el'.
Its value is

3

Documentation:
Visibility of actions when command `antlr-hide-actions' is used.
If nil, the actions with their surrounding braces are hidden. If a
number, do not hide the braces, only hide the contents if its length is
greater than this number.

You can customize this variable.