SciTE is an extendable development environment for producing source code and markup language files. Your preferred tools can be integrated into SciTE.
SciTE is customised through editing text files containing a list of properties in order to allow control with flexibility.
Available for 12 years on Windows and Linux, SciTE has now been implemented for macOS.
Documentation in OS X Help Viewer format is included with SciTE and shared documentation with other implementations can be viewed here.
SciTE may be purchased from the Mac App Store.
With version 3.1.0, SciTE supports the OS X 10.7 sandbox. This may require explicitly allowing access to particular files and directories when using external tools from within SciTE. There is some sandbox documentation.