Currently if you have a Task open in full screen or side panel view and you are looking at the Subtasks for that task, you have to toggle on which custom fields you want to show in the Task view for the subtasks. That's all well and good, but it doesn't save that view. As soon as you go to another task in the same list, you have to do that same process to see the same custom fields for the subtasks again. Same if you go to a different list and come back to that same task, you have to repeat the process all over again.