gnus-sum-thread-tree-single-indent

gnus-sum-thread-tree-single-indent is a variable defined in `gnus-sum.el'.
Its value is

""

Documentation:
With %B spec, used for a thread with just one message.
If nil, use subject instead.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 22.1 of Emacs.