The Tables filter group in the Filter Pane of the Impact Analysis - DB tab consists of a checkbox list with search filter:
With this filter, you can limit the displayed BI data to the nodes which are stored in the selected database tables(s).
Start typing a table name you are looking for in the search control, and the list will be limited to tables that contain your input.
There is an additional item (All) in the list of tables. Use it to toggle between all tables being selected and all tables being unselected.
If all tables are selected, or none of them, then the Tables filter is not applied, and it does not limit the data displayed.
See also