I'm using Fiddler v4.6.20173.38786 (Built: Friday, September 15, 2017). When I click on the Customize Rules menu entry there is a message box that says "Unable to load Fiddler for code-completion support". After I click OK to that the Fiddler script editor will open normally.
There is no registry key InstallerSettings after installing from Administrator in HKCU\SOFTWARE\Microsoft\Fiddler2
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Everything described above is still an issue in build Dec-14-17 v5.0.20173.50948 installer which is the latest version.
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And code completion doesn’t work.
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