Allow granular baseline adjustment

[DCEW]

Allow baseline adjustment per specialty, ungrouped. Feasible to offer grouped by default but with an option to expand to ungrouped?

[DCEW]

Linked to this spike

[matt-dray]

This was unassigned in sprint 18; I'm removing it from the sprint board for now, given other things to get on with in next sprint's major-version release. Do add back in for discussion at kick-off if this is something we need to do (though I note it was labelled 'low').