Yes! With the close icon styling options in the builder, it's possible to edit and even remove any campaign's default close X icon.
To access the close icon's settings, head to the campaign's theme tab and they'll be found under the "Close Icon" options:
Here, the icon's thickness, size, color, and background can be edited, as well as disabling the icon altogether.
Being able to remove a campaign's default close icon is a great feature for gated content, so creating an alternative close button could come in handy.