Slack extension with Stylus. Shorten message with the :complete: reaction icon.

slack-shorten-with-complete-reaction.scss

@-moz-document url-prefix("https://app.slack.com/client/") {
    /* Insert code here... */
    [data-qa="message_container"]:has([data-stringify-emoji=":complete:"]) {
        .c-message_kit__blocks {

            max-height: 20px!important;
            display: block;
            opacity:0.3;
            overflow: hidden;
        }
        .c-files_container {
            height:20px;
            display:block;
            .c-message_kit__file__meta + div{
                display:none;
            }
            img {
                display:none;
            }
        }
        .c-message_kit__attachments{
            display:none;
        }
    }
}