Rancher

This is absolutely true. There is not only a big need for complex scripts and non-Latin typesetting at the document level, but also at the paragraph and word level as well. It really needs to be considered from the beginning, not as an add-on down the road.

I am guessing the answer will be "no; buy new licenses," but is it somehow possible to transfer my Mac-based licenses for Affinity Photo and Affinity Designer to Windows editions? I purchased the Mac editions via the Apple iTunes store.

The easiest thing to do is just select the text and change it to Heiti (or whatever Chinese font you wanted in the first place). The boxes just mean that those characters are not present in the font you are trying to use (Helvetica in this case). The other question is that if you know Helvetica does not have Chinese hanzi in it, why would you bother trying to format Chinese text in Helvetica rather than Heiti to begin with? Some applications, such as Photoshop, will pick a font that does (often Lucida Grande), but that is hardly an informed design decision.