I do all my ModScript and AppScript work using Notepad++.  I use the "VBScript" configuration settings and save the contents to a local file.  Then in Composer click the "Import" button.

FWIW, we have to keep all scripts in our on-site GIT system.

PM Thompson  , thanks for responding , I can;t see the configuration settings of VBScript in Note++

I don't see "VBScript" either, but I assume he meant under Languages > V > Visual Basic. That is the closest one I see and should work pretty well.

In one of my classes that I took for SBM scripting & orchestrations, I was given a plugin for chiascript. I use that for modscripts, and I use visual basic for the old app scripts. I'm not sure who to contact to get it now, or if it's been updated since I got it, as it's been several years. 

In NP++, under "Settings" select "Style Configurator".  Scroll down to "VB/VBS".  In "User ext" add the file extensions you use for AppScript aka TeamScript.  I started using "TSC" for AppScript files and "TSL" for AppScript "libraries" (i.e. files containing constant definitions, utility functions etc.  "TSL" files are included by TSC files.

Technically this is just syntax coloring and not a NP++ User-Defined Language.

I'm trying to transition to the free MS "Code" editor. 

Chaiscript language highlighting and autocomplete can be found here:  GitHub - ChaiScript/npp-chaiscript: Notepad++ support for ChaiScript language