I assume that the slider tab in your version was a bug. Joffm's screenshot is not showing the question type N, but "multiple numerical input", which is type K (where the slider option is supposed to show).
And I just checked in the demo which runs 4.4 RC3 and there is a slider tab for the "multiple numerical input" question type (NOT Array numerical). I can't really post a screenshot, because you can either only see the question type or only the slider tab. But in RC3 it is there. I would be surprised if it isn't in RC4.
And as I said, you WILL encounter issues in LS 4, which is why it is labled as unstable or under development. However, this doesn't seem to be one.
Infos on what a question type can do are available here in the manual:
www.limesurvey.org/manual/question_types
E.g. here for the "Numerical Input" there is nothing about the slider layout:
www.limesurvey.org/manual/Question_type_-_Numerical_input
But here for the "multiple numerical input" you can read about the slider layout:
www.limesurvey.org/manual/Question_type_...merical_input#Slider
As I said, the appearance of the slider tab in your "numerical input" question (if it was there), was probably a bug in your old version of this unstable branch. Seems like they fixed this in newer versions of that branch already.