Why is this feature important to you - For general categories, users have to refer to external presentations to understand the data they need to include. Having a description field for general categories available in the timesheet view as a column will help them understand what the category should be used for.
How would you like the feature to work - Timesheet view needs to have customization of adding columns in layout templates
Current Behaviour - As of now, there is no way to customize a timesheet. Alsthough we can customize Timesheet lists, there is no way to customize what can be shown in the timesheet itself