I have noticed that there are two places to include media items for a source-citation. The first is with the master source: creating a new source also provides the ability to attach a media item. Then there is also the citation dialog which allows a separate set of media to be attached.
My question is: what is the difference? Should I prefer one over the other, or use both? Does one show up, and not the other, when I publish a chart/book/etc?