pfSense Diagnostics -> Packet Capture support for loopback interface
I can't overstate how useful the GUI Packet Capture feature is for debugging all variety of networking issues, but it's missing an option to capture traffic on the loopback interface. This would be a very useful and, I believe, fairly simple feature to implement.
#1 Updated by Alfred Barnat about 2 years ago
In particular, in order to debug a problem I was having with the HAProxy and Acme packages (#7519), I ultimately ended up having to just do this manually on the router. Not a big deal, but it may have short circuited a couple hours of debugging if I had just been able to try this directly from the GUI at an earlier point.