WP File Manager

Name	Action
..
block.json	Edit
editor-rtl.css	Edit
editor-rtl.min.css	Edit
editor.css	Edit
editor.min.css	Edit
style-rtl.css	Edit
style-rtl.min.css	Edit
style.css	Edit
style.min.css	Edit

Editing: editor.css

.wp-block-columns :where(.wp-block){ margin-left:0; margin-right:0; max-width:none; } html :where(.wp-block-column){ margin-bottom:0; margin-top:0; }