Can the sort operation costing 43.7% be elliminated from the plan ?
With that said, yes it is possible to eliminate this sort by creating a suitable index on the TIMESHEET_LINE table. A suitable index could have TIMESHEET_HEADER_REF as its leading key, with the other needed columns as includes. For example:
CREATE INDEX IX_dbo_TIMESHEET_LINE__TIMESHEET_HEADER_REF ON dbo.TIMESHEET_LINE (TIMESHEET_HEADER_REF) INCLUDE ( TIMESHEET_LINE_REF TIMESHEET_GROUP_INPUT_TYPE_REF, TIMESHEET_ABSENCE_REF, MONETARY_VALUE, MONDAY_HOURS, TUESDAY_HOURS, WEDNESDAY_HOURS, THURSDAY_HOURS, FRIDAY_HOURS, SATURDAY_HOURS, SUNDAY_HOURS, WEEK_HOURS );
Alternatively, if TIMESHEET_HEADER_REF and TIMESHEET_LINE_REF for a unique key, you could consider creating the index as UNIQUE on those columns and INCLUDEing the others. The general idea is the same: provide the required order using the index key, and provide the other columns as keys or includes as wider considerations dictate.