Cascading inputs in Splunk dashboards allow the selection in one input (like a dropdown, radio button, etc.) to determine the available options in the subsequent input, creating a dependent relationship between them. An event handler can be configured to reset subsequent inputs based on the selection made in a preceding input (Option A), ensuring that only relevant options are presented to the user as they make selections. This approach enhances the dashboard's usability by guiding the user through a logical flow of choices, where each selection refines the scope of the following options.