cols

cols
Type:integer
Scope:Display
RenderType:textTable, default

Abstract value for the width of the <textarea> field. To set the textarea to the full width of the form area, use the value 50. Default is 30.

Does not apply to RTE fields.

A simple text editor with 20 width

../../../../_images/Text4.png 
'columns' => [
    'text_4' => [
        'exclude' => 1,
        'label' => 'text_4',
        'description' => 'cols=20, rows=2',
        'config' => [
            'type' => 'text',
            'cols' => 20,
            'rows' => 2,
        ],
    ],
]