There is, as I said before.
Usually searching for specific parts of the message works quite well to find the text you want to customize.
So you can search for the title “Flagged post removed by staff” to find the text you want to customize and then search for a part of the body like “This post was flagged by the community and a staff member opted to remove it.” to find system_messages.flags_agreed_and_post_deleted.text_body_template. Keep in mind that those texts are used for all flag types. The {flag_reason} is replaced by one of the flag_reasons texts. The most important one for you is flag_reasons.inappropriate.