Allow single selection of transformer child endpoints

[sh-rp]

If the user only selects the child of a parent child relationship, do not render the parent and add the path param to the pre-filled params

[sh-rp]

@rudolfix there was a ticket in the original repo that said when selecting a child endpoint, the parent should also be rendered in a deselected state (which is how I have implemented this now). Do you want this behavior to be changed or should I keep it the way it is?