The list of filters has gotten too long, the filters are often not self-explanatory and all the tooltips only repeat the names of the filters.
Ideally we would only offer a few important filters with helpful tooltips and add a function for adding self made filters.
I am giving this wishlist priority for now.
For the current filters we would need a list of the names and what kind of filters they should use. Most filters are defined in libkleopatrarc. But honestly I think replacing the preset filters with a little "filter" menu that exposes the KConfigBasedKeyFilter rules to the user would just make the most sense. But this is a little bigger task, so wishlist for now.