I use the agenda widget on my phone's main screen and make heavy use of BC2 tasks and subtasks. Currently, I can't tell on that screen if a task has subtasks without either going into the task or setting the "indent subtasks" option which causes all the subtasks to be expanded which for me means I can usually only see one or two tasks without scrolling. For me, a really useful feature would be to give tasks with subtasks an "expand" button and hide or disable the "expand" button for tasks without subtasks.