For instruments like trumpet and horn, fingering is used to show which valves must be depressed to produce a specific note.
You can enter fingerings for valved brass instruments into the fingerings popover as numbers without any separation. For example, enter 12 for a C♯ on a trumpet to indicate that the first two valves must be depressed.
By default, Dorico Elements automatically stacks fingerings added to notes on brass instrument staves vertically. They are shown with no separator by default.