From version 3.7.0.0, Lightning Forms and Lightning Tools Actions now have a feature that allows you to debug your complex configured actions and check inputs/outputs in the console on the SharePoint runtime.
To use Debug mode, you need to enable this option in the design time, go to SharePoint runtime, open the console tab in the developer tools (F12) and execute your action.
Note: This mode can be activated on the current site only.
Debug mode option is available in the Action Builder for Lightning Forms and Lightning Tools Actions.