Hi its called onepage_promo ... thing is we noticed you need to add that one first ... before you add the onepage_promo_top otherwise you can't hit enter.. this is what I would call a Joomla bug... you will see what I mean when you try.
But if you already added the onepage_promo_top .... when you start typing onepage_promo you cant stop there. .. ifg you hit enter it will automatically select the onepage_promo_top ... so its more about how therse dropdowns work there.,
Not sure its actually a bug, just a UI issue. But will report it later.
I just tested and upon typing onepage_promo Joomla tries to assume & select the nearest module position for you, so if you hit enter, it loads up onepage_promo_top (when you have already set the top module).
BUT, if you type onepage_promo into the module position and before hitting enter, click your mouse on the text field you just typed "onepage_promo" in, this deselects the "onepage_promo_top" module position and allows you to hit enter.