Ok,
etwas Suche und die Lösung ist scheinbar gefunden (siehe: Bugzilla):
Code
Config Editor:
view_source.editor.external = true
view_source.editor.path = C:\Program Files (x86)\Notepad++
the same for "C:\Program Files (x86)\Notepad++" or "C:\\Program Files (x86)\\Notepad++"
Actual results:
The external editor isn't invoked.
Expected results:
The external editor should be invoked.
This works fine in TB 60 beta 2. I have 64bit Notepad++ so I set
C:\Program Files\Notepad++\notepad++.exe
This only affects viewing the JS source via Tools > Developer Tools > Error Console.
We're still working on "View Source", see bug 1439021.