Result of the action should be available to the next for each action (if any). The result is available in the action data filter (result and toStateData) by using ".". But, unless stored in a temp variable, it is not available to the next action, which reduce to almost to zero the chances of using action chains. Rather than forcing to add a temp variable in toStateData (a variable that will very likely need to be filter out explicitly later), lets define one automatically with the result of the action.

The expression to retrieve the result of the processing of the previous item is $WORKFLOW.prevActionResult