MC4SF_LAYOUT
We will automatically attempt to add the Mailchimp Members component to the default page layout. However, this is only possible if the Salesforce Contact or Lead layout already has a lightning page activated. If we cannot automatically add the layout, you we get this maintenance code and will need to manually add the components. You can find more information on that here: https://www.beaufort12.com/mc4faqs/how-can-i-manually-add-mailchimp-to-my-page-layouts