1. In Dorico, it is easy to create time signatures and key signatures on just a single staff, by holding down the Alt key during input.
  2. To input a time signature on a single staff, press Shift+M to open the popover and type the desired meter as usual.
  3. If you hold down Alt while you press Enter, the time signature will be input only on the selected staff.
  4. It works for creating time signatures using the mouse as well. Simply hold down Alt while you click.
  5. The same method can be used to create a key signature on a single staff. Shift+K opens the key signature popover where you can type as usual. Holding down Alt when pressing Enter creates the key signature just for that selected staff.