If Listener output was a string, you can click on it and copy it to the Listener input field, just like expressions you've entered previously.
Not all Lil values can be losslessly represented as strings; functions, for example, normally travel with invisible linkages to their closure, and Interface values are not necessarily serializable. Data can generally be represented by using "format" to convert it to JSON:
"%j" format x
As in Lilt, in the Listener you can reference the result of the previous evaluated expression through the variable "_" (just one underscore). This variable is automatically rebound every time you evaluate an expression. It's also very handy for getting context you can explore interactively out of a panic[].