Hi @Mark_U ,
Wow that's harder than it looks.
I was thinking initially the query list action and then possibly a retrieve item action inside a loop to get more details. But the path, URL, or encodedabsoluteURL properties are not returned in the object for libraries.
Get a file action does not help as it only returns a file object.
I think you will need to use the 'Call a SharePoint web service' action and contruct a query to retrieve the list item by it's ID.
If you have a look at the help page: SharePoint Online - Call a SharePoint web service (nintex.com)
Then see the example on that page to call and item and extract a property that should get you started.
Apologies I don't have time this morning to mock up a working example.
I think there is also a feature request here to get Nintex to expand the SharePoint online actions to create 'query a library' action and return more details about the files in a library. If you take a look at the check out files action you can see that the conditions also include an option to navigate subfolders. So that logic should be included in the action too.
The fact that you have to call a webservice just to get the path of a document in a sharepoint online library is crazy.