Hello,
The team is not currently considering providing an extension option. Still, I've understood you are looking for a way to decrypt an encoded request or response body from what I've understood. If that is correct, this is a functionality already present in Fiddler Everywhere for many known encodings (like gzip, deflate, etc.). The decoding is enabled by default for all inspectors except the Raw (where you could manually decode - refer to this documentation article for more details on how to decode in the Raw inspector).
Please do let me know if you are experiencing other issue or if you want to decode a specific encoding which is not yet supported in Fiddler Everywhere.
谢谢
我的意思不是解码（decode）问题，我指的是发出的请求body是经过加密处理的，比如AES加密，请求body就是一串密文字符串，以前Fiddler可以使用扩展DLL，自己实现解密展示到Fiddler->Inspectors里，现在FiddlerEverywhere希望也能勾提供扩展功能，这个功能真的很实用，对我们软件测试人员有很大帮助，能够极大的提高工作效率。
期待ing~
Thank you for your feedback! I can confirm that at this moment, the feature to work with external DLLs is still not supported in Fiddler Everywhere. I am posting an automatic English translation of your issue description and marking it as a feature request to be researched further by the team.
Translation
I don’t mean the problem of decoding. I mean that the request body is encrypted, such as AES encryption. The request body is a string of cipher text. In the past, Fiddler could use the extension DLL to decrypt and display it by itself. In Fiddler->Inspectors, now FiddlerEverywhere hopes to also provide extended functions. This function is really practical and helpful to our software testers and can greatly improve work efficiency.:
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FiddlerEverywhere什么时候开放Extensions功能？就像Fiddler一样，可以加载用户扩展的插件。因为测试工作中捕获的请求body和响应body是加密的，需要解密处理显示在fiddlereverwhere里，如果不能自定义扩展功能，抓到的也是密文，没有什么实际意义。