I think it would be useful in some cases to create an object without opening a new page. InMx7.17 this throws the following error in the modeler
"Select a on click page for this action button"
An example how this can be used is a page that shows a list view and a there is a button to add a new item to the list. The new object is shown on the current page and can be edited inline, which is better than a popup in some cases, for example if the user is already in a popup.