How to remove the thinking-trail-history?

I don’t remember how I enabled it, but I don’t want the thinking trail history thingy anymore. Does anyone know how to disable it?

Here is the image of what I am talking about(Look at the top left corner):

Okay I got it. It is a part of the experimental feature(breadcrumbs). Not sure if it is very intuitive for someone coming from “A > B > C” world though.