On Tuesday, June 14, 2016 at 8:54:16 AM UTC-7, Dan Marotta wrote:
I've noticed with the latest versions of XCSoar that, while circling, a
blue line sometimes appears across my track as though providing some
kind of guidance or information. I've gone through the latest manual
and can't find anything about it. Do any other XCSoar users have an
idea of what it's for?

--
Dan, 5J

One of the most useful features of XCSoar, the curvature of the blue line indicates the forward path of the glider and it varies based on the bank angle - in real time.

You can use it to adjust your bank angle in order to accurately intercept the location of best lift you had gone through before as you circle.

David