The Component library should be placed on a tab under Projects, Content and Components, or merged to Components. I think it's used enough to deserve its own tab.
I've just found a post on ubuntuforums in which people complains about the lack of commercial components on Qucs. Placing the components library on a more visible place would avoid such mistakes and help new users get the best out of Qucs.
OTOH, playing a bit with Qucs and reading some manuals and part of the huge documentation (I learned the MNA method thanks to Qucs doc, even before I knew about Qucs), you can easily find where the components library is.
I agree with this, I also think the components library is too well hidden.