When trying to enter to run a Box migration, the following error is shown:

Sharegate.Common.Exceptions.SGNotSupportedException: The Box bookmark with the name 'Name' that targets 'site URL' will not be migrated because it cannot be converted to a document within SharePoint.

This error occurs because Box Bookmarks cannot be opened from SharePoint, and are not currently converted to a proper document type.

You can add the bookmarks by adding an URL column to the destination list in SharePoint and creating the items manually.