I'm using Fiddler [Oct-03-19] v5.0.20194.41348 on Windows 7 Enterprise. The AutoResponder panel has changed from older versions and no longer displays properly if the size is narrow. For example in the attached screenshot you can see no scrollbars or dropdown. They seem to have a minimum size of 850px right now. That is way too wide. I find it very difficult to use Fiddler when the panel is too wide because then I can't see the connection entries easily. The size in the screenshot is what I normally use the panel at and it works fine in older versions.
As a workaround I reverted to older version Fiddler [Jun-04-19] v5.0.20192.25091. Also I was left with a bunch of errant StringToMatch[xx] entries, not sure what that's about.