Visualize/graph: Better explanation

[roschaefer]

• I'm submitting a ...

  • user interface improvement

• What is the current behavior?
  There is a little explanation below the header. It's not recognizable and does not explain well, how the similarities are computed.

• What is the expected behavior?
  I should see a visually recognizable info box, explaining how the similarities get computed and some details (e.g. only the best 500 similarities are shown)

• What is the motivation / use case for changing the behavior?
  Clarity.