Awesome
RADSplit
Dockable Split-Screen Editors for RAD Studio (Delphi and C++ Builder)
Important Notice:
As of mid-2019, I am no longer able to access the Embarcadero Technology Partner program. I presume this means that my Partnership has been revoked. Consequently, I will no longer be able to maintain this project for new versions of Delphi. I will, however, actively review and incorporate Pull Requests where they introduce support for new versions of Delphi.