This custom CSS tester allows you to load a custom CSS to a YouTube Live Chat Comment page on your Web browser so that the CSS customized version of the page can be inspected on the browser.
The CSS loaded to the page can be debugged with browser's built-in developer tools (Hit F11 key on many popular browsers.).
Please start in the extension's option page to set-up a Live Chat comment URL. Once a comment page is opened on a new tab, the extension's popup page can be used to temporarily edit and hot-reload the custom CSS inserted by this extension.
Support Page: https://kii-memo.blogspot.com/p/cas-akaji-bot.html (In Japanese)