1. Open the inspector
  2. Select the "main" node
  3. Turn on the grid inspector
  4. Make sure you have the "display line numbers" checked
  5. Select the "b" node in "main"
  6. Focus the "-1" in the grid-row value
  7. Hit ↓ to decrement it multiple times
  8. See the line numbers disappearing in the grid inspector, and eventually, at "-4" the whole inspector disappears