ChemDraw

ChemDraw is a molecule editor first developed in 1985 by David A. Evans and Stewart Rubenstein (later by the cheminformatics company CambridgeSoft). The company was sold to PerkinElmer in the year 2011. ChemDraw, along with Chem3D and ChemFinder, is part of the ChemOffice suite of programs and is available for Macintosh and Microsoft Windows. 
File format.
The native file formats for ChemDraw are the binary CDX and the preferred XML-based CDXML formats.
ChemDraw can also import from, and export to, MOL, SDF, and SKC chemical file formats.
Plugins.
SDK for ChemDraw enables third-party developers to write plugins. For example, - Quick HotKey helps to set up HotKeys in interactive mode, instead manually editing of text file. The Plugin site
appears to have been abandoned.