I like using a combination of describe-face and customize-face to adjust the appearance of my working environment. Sometime this workflow fails when I want to change the face of a location I can not reach with the cursor; mode-line, header-line, magit-blame headers etc. Most of the time, I can trail and error my way to a solution but sometimes I get stuck (I didn't know the header-line existed until yesterday for instance).

Is there a convenient way to describe the face of a location in a frame which is not reachable by the cursor? By means of a mouse for instance.