You can easily change or add most any fields into the generate bills and bills grids. This example goes over how to add different columns to your Generate Bills page.
NOTE: THIS REQUIRES ADMIN PRIVILEGES
On the matter form, find the field you want in the grid, then In chrome, Right click 'Inspect' directly on top of the field.
From the chrome window that opens, make a note of the field type #. the part after the dash is the field type #. The 1001 is the Item type #. For a full list of Item and Field types see this KB Article. Below, we will use the 1000965 value.
Next, go to the system Settings>Config File Edit>Generate Bills Grid (or other grid you are trying to change) and find the column name you want to replace. If you want to add a whole new column, copy everything from an existing section from the <GridColumn> to </GridColumn> and modify for the new column.
in the Item Type value, change the existing number to '1000965' and change the label as you desire, ie, 'Paralegal'
Click save, then reload the Generate Bills Grid. Your new field shows up.
Note: If you add more fields, you may need to adjust the percentages of each column to add to 100% if you don't want to end up with horizontal scroll bars.