In the Inheritable Attributes section of the options, there's the checkbox "Continue to update subtasks as parent changes". I set Category to be inheritable and then selected this option. Next, I created a task, and then created several subtasks. I then assigned a category to the parent task. In the tasklist, the category appeared in the Category column, but only for the parent task. I clicked on each subtask and saw in the edit field that the category has been assigned to them. However, the Category column was blank for those tasks in the tasklist. There was no way to cause the category to appear in the Category column, outside of closing and restarting TDL.