You can use the "Quote" feature in the task to add file reference or note reference as supplement to the task. The method is as follows:
On PC:
Open a task in project > "Quote" > Select "Add note reference", "Add file reference", or "Upload file" to quote the supplement to the task.

APP:
- Tap "..." icon in the upper right corner of the project to expand the hidden options > "Project task";
- Enter the "Task" you select > Click "Edit" in the upper right corner > "Quote" > "Add" > Select "Add file reference" or "Add note reference" to quote the supplement to the task.