Creating a new item in a list every time an item in a different list is added

I would use a Query List operation that would cycle through each item in a list.  My guess is you need to check this regularly, so a site workflow would be your answer.  The Query list can be filtered to look at a specific field and only capture those items within the list that meet your criteria.  In your case you want field XXXX to equal Pending Scheduling or Completed.  So probably run a parallel action on the onset that does two different queries.  Once you identify which list items meet your critearia, you can perform a "Create Item in Another Site" action to add the corresponding information to the new list (when you have a Pending Scheduling) or "Delete item" action to remove the list item when Completed occurs.   This link gives a real detailed review on creating query list actions and the power it can perform.  I used this to create several workflows that review through all kinds of lists.  I found it very helpful.

https://community.nintex.com/t5/Community-Blogs/Queries-and-Collections-and-Loops-Oh-My/ba-p/82404