Many thanks for replies to my post earlier in the week. I’m getting there…!
Having used Sibelius since about 1996 on the school’s Archimedes computers, it’s ingrained into my being, but starting to adapt nicely.
I can’t for the life of me, though, work out how to add to notes in one voice at the same time. For example, I want a middle C plus an E natural a third above, sounding at the same time. In Sibelius, it would have been as simple as selecting the C then (I think) clicking shift-E and the extra note would go in above.
If you’re clicking in with a mouse you need to hit Q or click the chord icon (the triad) in the left panel.
Alternatively use Shift-I, the intervals popover, and type 3 for a third above or -3 for a third below. You can also stack, separating using a comma, and you can get specific about what type of interval you want, e.g. -d3,a4 will give you a diminished third below and an augmented fourth above.