Frequently I think to myself ‘I’m sure there are files in that empty folder’ and then realise it is filtered by a term in the search box.
Not a priority at all (as somebody has said before - function before form) but could the fact that a folder is effectively filtered be signified in some way? Perhaps a slight change in colour of the background of the upper window or similar. I know I could just look up into search window - but useability is partly about removing those little jags before you realise you are doing something wrong.
I’m still sometimes caught by this “empty folder” problem too. I think the problem is that my focus is on the Records List pane, not on the Record Viewer pane. I may not immediately see the “big letters” there any more than I immediately notice that the search box is not empty. I think the suggestion of coloring the background in the Records List pane (or some similar indication in that pane) is a good one. Or at least make the “big letters” red so that they visually “pop out” more.
EagleFiler 1.4 shows the records list in yellow if it’s empty due to a search that found no matches, and it adds an esoteric preference for clearing the search field when you change sources.