Category

Bonsai Outliner for Windows > Item Details > General Tab > Category

Categories provide a customizable attribute that can be used as desired.  Each item in the outline can be assigned to a category, or left unfiled. 

The outline can be filtered on category.  For example, you could use the categories with a To Do list to indicate the best time of day to perform the work.  You could then filter your To Do list on time of day.

Note:

There is a 15 user-defined category limit for compatibility with handhelds using the Palm OS.