This has been implemented already.

When supporting websites, it's a pretty common thing to look for recently changed files. A filter on date would be a tremendous help for this!

OK, maybe :-)

Include the ability to filter out the list of files displayed in both the panes based on a "file pattern mask", "file size", "creation date range", "rights", "owner", etc... WSFTP has the feature to narrow down the list of files displayed by a file mask.