AceProject does not support multi-levels of tasks. It can’t “understand” a task as being part of another.
There are two workarounds.
The first is to create AceProject “Task Groups” ( or “Task Types”) in your project to represent your “main tasks” and then associate your “subtasks” (AceProject “tasks”) to the proper AceProject “Task Group” . That would allow you to filter and view all subtasks of a given “main task” and only these tasks.
You may also use a task numbering scheme to differentiate main tasks and subtasks (for instance, a main task could be #3, and its subtasks would be # 3.1, 3.2, 3.3, etc.)
In other words, here are the possible workarounds: