Feature has been requested/discussed several times in the forum. Here is a relatively recent thread, where the developers have declined it (giving reasons):
Topic #62603
If you are interested in workarounds, can add category name to any empty field (e.g. package comment) and use the search field in the bottom toolbar to quickly filter the list using it as a search term. Can also enable the 'comment' column in the download list to view/sort by that value.