Yeah, you could have a field representing the currently selected item.
You could also, when building the second list, populate those items into a list contained within your TMainTask type. Logically, a TMainTask can contain a list of TSubTasks.
You could also, when building the second list, populate those items into a list contained within your TMainTask type. Logically, a TMainTask can contain a list of TSubTasks.