It would be awesome to be able to use regular expressions, or at least some sort of wildcards, in searches and filters in Thunderbird. That would go for all text-based search criteria, so headers, message body, etc.
I haven't really started to explore Tbird addons yet, but I will certainly look at ones that feature regex searching. That said, I'm more inclined to use saved searches than filters to sort messages, so filtaquilla might not be exactly what I'm looking for. I'm just starting to explore using Thunderbird as a daily driver after many (many) years of using more old school text-only mail apps with features, like baked-in regex searches, that are targeted more toward 'power users.' So, my suggestion is really just a first impression reaction. If there's a way to get what I'm looking for through an addon, that's great.