It's totally fine as far as conversational English is concerned. Although the personal pronoun I at the beginning of I edited that in (since the phrase is in the past tense, it means I already did it) is omitted, it's nevertheless understood. It's common practice in spoken English to leave out little words like personal pronouns that go at the beginning of a sentence. Here's the most archetypal example of this practice I can think of:
— Wanna go out tonight?
— Yep. Sounds good. Let's go to a restaurant.
The phrasal verb edit something in means to add something into a piece of text, video or any other type of medium. Edit something out would be an expression that's opposite in meaning. If you edit something out of a piece of text, video etc., you remove it from that piece of text or video.
All swear words and other strong language must be edited out from the clip before uploading it to YouTube because some of our viewers are actually under 16.
— I'd like you to add this to the text.
— Alright, I'll edit it in.