Ordinarily, as new expressions are evaluated, the old ones sink towards the bottom of the table. (By default, the global variables X, Y, Z do not sink.)
If you want to keep a value or expression readily available:
To reverse the process:
It is sometimes useful to have a value or expression available in all the Snooper evaluation panes.
Whenever you open a new Snooper, that expression and value are present in its list of available values.
To reverse the process:
The expression will no longer appear in new Snoopers.
Similarly, the Unsave Everything command releases all the saved expressions.