I learned Cubase score when Sibelius was a twinkle. Took me a few weeks as I remember. And you do need prior knowledge of the several ways you can notate so it can be set up right. It’s good that it has bought into Sibelius as this will probably bring the notating style forward because with all the computing advances and communication improvements I believe, on looking at some old music in an actual book lately, that notation has sharpened up, become a little homogenous maybe, and the more popular styles have become more commonplace. Seeing that I think that it may be time that some choices could be removed from Score to make life simpler. It’s actually the setup in the first place thought that foxes the new user. It can be a little arcane to say the least and leave you scratching your head when you need that extra rest or accent inserted and you forgot where it was when you looked two months ago.
Once you’ve got Score though it tends to stick and it is VERY comprehensive.