The ArcGIS 10.5 Metadata Toolkit has been released on the Esri downloads site.
This toolkit provides documentation and software that allow you to customize the metadata viewing and editing experience in ArcGIS Desktop (ArcCatalog, ArcMap, ArcGlobe). Although some customizations only require editing of configuration files (no coding), others require the use .NET/WPF development tools.
ArcGIS Metadata Toolkit 10.5.x
