Overview and structure of processes

After looking around at the learning

material, I'm still not sure how to go about making a full overview of all

processes and then drill down into to more detailed levels. Is it possible to

make this kind of tree-structure where you have sub-processes within

sub-processes?

Where do I make that kind of overview,

because when I open modeler, it seems to me that I'm only able to make

individual processes, without connecting them to each other in a hiearchy form.

Secondly, do I need studio to connect data that a process uses? I work on a project which is primarily description of processes and the data that is needed to run the process and do not need any automatication.