How do i make my own synths in Sibelius
Sibelius is a notation app, not a DAW and doesn't have the ability to make synths. So no, it's not possible.
In fact, a DAW probably won't have the ability to make a synth either, but it might have one built in that will do what you want.
In fact, a DAW probably won't have the ability to make a synth either, but it might have one built in that will do what you want.