Broaden sorting to accommodate more fields

The sorting rules should be also available for Grouped by fields as this is where you can define the a position of the group headings in the table. Each grouping level should be able to define its sorting criteria.
In case of the Focus area grouping – I have no control on the order of the grouping sections in the report ( default sorting = alphabetic A-Z) but this is not how we want to see it.
BTW there is no means to setup a custom field for the Focus area level, so it might be useful to expand the Focus area definition record by e.g. sorting keys or additional useful data such as ownership ( org, dept), numerical reference, etc .. which would help to manage the ordering and filtering much better. Is it possible to define a custom field as sortable value so that the data in the table ( strategy table) can be sorted by this field? There is a custom field ID ( text value) by which I would like the report is sorted by, but there is no option for this. Assume that would require the field is mark as sortable and index is created.