Hi
The code you have looks good to me. I ran a quick test in my environment and find it is working fine. I basically copied the pleCustomActionEx.cs and made pleCopyCustomActionEx.cs and plePasteCustomActionEx.cs.
The first action class Perform method is simple: just create an ActionResult, set the OutParameters and return the ActionResult.
The second action class retreive the parameter the same way you did. Just make sure ActionName part matches what you defined when configuring the first action.
As long as all chained actions within the same listform and in specific order (First action first which sets the action result and the second action follows to retrieve the parameter), this should work. It does not work across different forms.