I think Johan, since it is not possible to prevent the user from changing the configurated sort settings, it is not possible to retrieve the last object in a micro flow. However when there is a functionality to retrieve the current search settings this could be possible. Maybe this is possible using a little Java code. I think Johan is more capable of answering that question.
Maybe I have another solution. Since there is no edit button anymore, I suppose there is no button linked to the double click event. You could link a new button with edit location set at 'InlineAtTop' to the double click event.
I hope this simple solution is of some use.
If you tab to another row the inline editing grid will commit the changed object. Hence, you can add an after commit event creating a new object (with refresh in client on true). This will create a new object and refresh the inline editing grid.
If you only want to create a new object after the last row you have to add a check to your microflow somehow determining that your are dealing with the last object. For example, use the same query and sort options as the inline editing grid and compare the committed object with the last object from the retrieved set.
I hope this gives you some directions for a solution!