"Groupings" of Option Values: are they actively used?
Feel free to use it, some other extensions (eg. CiviHR) are using the grouping field as well as the core

+-----------+-----+
| grouping  | t   |
+-----------+-----+
| NULL      | 872 |
| Absence   |   3 |
| Avery     |  11 |
| Closed    |   1 |
| Opened    |   2 |
| Timesheet |   9 |
| Vacancy   |  11 |
+-----------+-----+