Glad to know that I'm not the only one who found rather aggravating the lack of a single-testimonial view. And the impossibility to sort by category. Again, your solution of turning testimonials into regular posts solves all this. Quite elegant. But it stresses how flawed the Testimonials section is.
While we're at it, hoping that someone from the Stay theme design may accidentally stumble on this thread - or, more realistically, that some other poor soul like myself may need help :
I would think it nice if the technical info should include the particular meanings given to "Excerpt" and "Citation" by the Stay authors. English is not my native language, and I had to work quite a bit on those sections of the Testimonials admin page.
According to the Oxford English Dictionary, an "excerpt" is "a short extract from a film, broadcast, or piece of music or writing". It's not obvious, then, that if you want your testimonial to be published in full, the Excerpt section is where you should enter it. Rather an unpleasant discovery after spending hrs of work entering your testimonials.
A "citation", according to the same source, is "a quotation from or reference to a book, paper, or author". How that became the testimonial author's name, I can more or less comprehend, but words like "Name" or "Source" would have saved me several hours of easily avoidable editing. Am I really the only non-native English speaker on WordPress? ;-)
I'm restricting my comments to the Testimonials section as it is the subject of this thread. But something could also be said about the maximum size of a featured image in a page, which is quite different from that of the same image as it appears in the slider. I would think this kind of info should be part of the basics given to the user, who otherwise spends yet more hours guess-resizing images until they display properly.
I'm not sure there is any way to suggest that the Stay design team add this info to their presentation? I find it rather off-putting. Especially when I compare with other themes I use for my other blogs (Oxygen and Forever) which are well-documented. Pity, as Stay is a really beautiful theme.