Currently, it appears that the AutoResponder rules are exported on the UI thread (i.e. when exporting a massive Fiddler AutoResponder rule set, Fiddler is "Not responding..."
With a large AutoResponder set, Fiddler's UI may become unresponsive for minutes.
I believe this also prevents incoming connections from being processed - if true, that is even worse.
If this does get done on a background thread, to keep consistency, perhaps the AutoResponder rules window should be "disabled" (greyed out) so no changes can be made to the rules while exporting.
It looks like the delay is because I was exporting to a heavy-volume network share. (20 seconds vs several minutes) - however, this could still be a problem for some
About 300 rules, the FARX is 320MB
How "massive" a ruleset are you persisting?