At this point, collider shapes can be edited only via Inspector and this could be quite time consuming. Having a gizmo that allows editing shapes directly in the scene preview would significantly speed things up.
This is done, now a new interaction mode button (with triangle icon) appears on the toolbar when selecting a collider and by activating this mode you can edit collider shape by dragging respective handles.
At this point, collider shapes can be edited only via Inspector and this could be quite time consuming. Having a gizmo that allows editing shapes directly in the scene preview would significantly speed things up.