Add child channels to other instruments

Certain instruments in Musescore have multiple child channels (as seen in the mixer panel) that belong to that instrument, e.g. strings have arco, pizz and tremolo channels, trumpets have a "normal" and a "mute" channels that one switches between using the appropriate staff text. Is there a way to add this feature onto other instruments that don't currently support it, for example, french horn mutes or tuba mutes?
More generally, is there a way to add custom child channels onto existing instruments, so soundfonts can be switched out for solos and such?