Waiting for UX input here: https://jira.magnolia-cms.com/browse/MGNLUI-5976?focusedCommentId=223406&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-223406

The Code Field Type's width is too small. 
There are three different sizes for the code field text box when used in different dialog positions. The most reasonable sized code field text box is when used on its own. When you use it within a composite field or collapsible composite field, the text field is too small to manage.

(Edit: This goes for all text boxes, not just "code" type. 6.2.1 does not have "collapsibleComposite" type but the small box problem still persists with regular "composite" fields. See additional screenshot) 

Steps to Reproduce
Create a dialog with a composite or collapsible composite field containing a text box (You can use the example on the attached Support ticket).

Expected results:
The text box should be large and easy to read.

Actual results:
The text box is too small.

Workaround:
Create a custom theme and implement custom css to make the box larger on the dialog

Notes:
The size of this field varies depending on where you use it. It is smallest when used in a composite field as seen on the screenshots. Happening in 6.2.1 as well.