The script editor has following features that make the code edition easier:
The API functions can easily be accessed by typing the first 3 letters (usually "sim"). Copy/paste and undo/redo functionality of the script editor is supported through a popup menu (right-click). When a script was modified, there is no need to explicitly save the changes: closing the script editor, saving the scene or starting a simulation will automatically apply the changes to the script. When a simulation is running, modifications to a given script will only have an effect once a new simulation run is started, except for customization scripts that will always apply changes once the editor was closed.
If you have recurring functions you wish to access from a given script, you can add following line at the top of your script:
In that case, make sure the file is named myExternalLuaFile.lua, and do not forget to distribute it together with your scene or model, since that code will not be part of a V-REP file anymore.
If you wish to use a particular editor to edit V-REP's embedded scripts, then refer to the entry externalScriptEditor in the user settings file system/usrset.txt. For proper keyword highlighting, auto-completion and call tip display, use the data in file v-rep_notepad++.zip (in the installation directory).