I would like to use a different editor for my game code than the default xcode (for mac). Specifically, I would like to use Atom, a free editor from GitHub which can be invoked by the shell command atom [file]. However, I see no way to change or add a new source code editor (I’m looking at [Editor] Preferences → Source Code). Trying to export the window gives me:
[/Script/SourceCodeAccess.SourceCodeAccessSettings]
PreferredAccessor=XCodeSourceCodeAccessor
I’m thinking that I have to add something like AtomSourceCodeAccessor somewhere else, but I have no idea where to even start looking. Am I on the right track, or did I completely misunderstand what this setting was for?
UBT let you compile without opening editor (Xcode/VS), it only use there compiler… means you can build in any editor by binding command line
UnrealBuildTool.exe ProjectNameEditor Win64 Debug "%CD%\ProjectNameEditor.uproject" -rocket
You probably will need to modify it for OS X 
I’m not looking to build my project at all - I’m actually starting from scratch right now. I stumbled upon this option and assumed it was for making my game code open in a different editor than Xcode… is that not what this option is for?
You are on the right track. XCodeSourceCodeAccessor is a plugin for the editor that is used to open source files in Xcode, jump to a specific line in code and to save all open documents.
Adding support for other editors would require writing additional plugins. Xcode one uses a simple AppleScript to open Xcode and perform operations in it, so I suppose that writing a new plugin based on that should not be complicated.
Thanks! Would you happen to know where XCodeSourceCodeAccessor is stored so that I can copy and edit it to use as AtomSourceCodeAccessor?
When you get the code from GitHub, the plugin source code will be in UE4/Engine/Plugins/Developer/XCodeSourceCodeAccess