Display and Probe a J Sentence Graphically

A verb has, in addition, a rank stack, a line for the shape of the result, and an optional selection line. When framing fill has been added to a result, two shapes are shown, as in the example below:

Until you select a result-cell, these values will be the same. If the cell you selected is a result cell of a chain of verbs, the selection will be transmitted to the other verbs in the chain, and cause them to display their contributing values.

Source: code.jsoftware.com