I have created a presentation using a template, where I created some copies of
the "Base Content Slide". 

Now when I try to create new copies, it always copies the first (and filled out)
slide, not that one which I select.

The root cause seems to be that all slides created via Drag&Copy have the same
name, and that Drag&Copy copies the first slide with the name from the selected
slide, which is not necessarily the selected slide