From https://bugzilla.mozilla.org/show_bug.cgi?id=1573542#c5:

When I click on "View Certificates" (https://bug1573542.bmoattachments.org/attachment.cgi?id=9085220), Firefox's main thread pauses and I get the Windows "Nightly is not responding" title bar modification thing.

Bug 1573542 is fixed (and the map thing which caused me to initially file it is much better!) but I can still jank the UI when I click on View Certificates (under Options).

I'm pretty sure I know why this would be happening (we gather the list of all certificates on the main thread, which can involve hitting the disk), but it would be nice to have a profile to confirm.

https://perfht.ml/36gh5NI (but of course when I tried it this time I didn't get Windows telling me Nightly wasn't responding ...)

Thanks - it's what I figured about finding all certificates on the main thread.