Is it possible to show tasks in a task list collapsed by default? And if so, is it possible to specify some tasks/sub-tasks as collapsed by default and others to be expanded by default?
By default, it is collapsed as group
and to check this setting > open your view > modify the view .
- From the above ribbon, select modify view >
- beside group check this setting
Regarding controlling to collapse some sub-tasks unfortunately it's not supported as out of the box but you can create another view to show your subtasks and set it as expanded .