How to implement nested instances in Mendix?

I have an Activity entity but requirement is for this to be broken down into sub-activities down to any depth (with reason but let’s say its recursive). So I have a relationship between Activity and itself and this looks like the first step. But how to build a form that allows input of these activities and child activities? I am presuming some sort of TreeView widget would be used. Has anyone done something similar? Care to share?
1 answers

The appstore has two treeview widgets and demo projects to try them. I created one of them. Both implementations allow the functionality you describe.