As of now the only way to print a task list is to use Googl'e web site, "Actions" menu, option "Print task list".
I know it's far from perfect as it doesn't print things like notes etc, and I am tracking a workitem to add such feature to GeeTasks.
If you could describe what you want to do with printed tasks it would help me design a better print feature.
As to separators, right now each task has the list name added in small print and brackets, like so:

A real separator would be better, although one problem with that approach is that if tasks re sorted by e.g. due date the separator has to disappear, so the current way of marking tasks will likely have to stay. I will see what I can do.