[Paul Stenning]

That is the lack of JavaScript support. The only drawback of not having that working is that in some cases one data sheet will be relevant for several sets but there will only be one copy of the file in one folder. This means that by just using the folder structure you may think data isn't available for your set when in fact it is.

Of course you could look up the data on the website which will show you all the sets it applies to, and the filename which is the path separated by hyphens. It takes a bit longer but the results are the same.

Unfortunately I have not yet found an open source PDF viewer that supports the JavaScript. If one did exist it would be a nicer solution.