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-rtl.css

.wp-block-text-columns .block-editor-rich-text__editable:focus{ outline:1px solid #ddd; }