To filter tasks using AND/OR/NOT:

1. Create a script that will return 1 whenever the task passes the filter conditions.
2. Create a calculated custom field that will return the value of that script.
3. Choose an existing task filter or create a new one.
4. Set filtering conditions for the calculated custom field.
5. Click the Subtasks tab.
6. Choose your filter.

• Adding a Custom Field
• Calculating Custom Field Value