I’m currently making a theme, and there is a line above the search bar which goes across the whole screen. It makes it look ugly and cut off. Is there any way to fix this?
toolbar_top_separator is what you’re looking for ? See https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/theme
Are you using Firefox Color to create the theme or are you creating it directly from the site?