You can modify the mapping of an existing Template-defined instrument (duplicate it first) to change how notes display on the staff.
However, Sibelius does not allow for mixing of sounds from different/multiple patches into the same instrument definition - it will only load one patch from the VDL library.
Otherwise, I'm assuming you're wanting to do this instead of being forced to use Instrument Changes?
As far as the Mixer, when using the Template, it's always best to leave everything set to (Auto) (well, with the occasional exception).
However, Sibelius does not allow for mixing of sounds from different/multiple patches into the same instrument definition - it will only load one patch from the VDL library.
Otherwise, I'm assuming you're wanting to do this instead of being forced to use Instrument Changes?
As far as the Mixer, when using the Template, it's always best to leave everything set to (Auto) (well, with the occasional exception).