Well to add to this, so thanks to #RunDll OutputDebugStringA I can now see that even though no errors are thrown, the code in the section shown above doesnt get called.
So in this instance, I can not detach these #At/#EndAt template code from the #Extension #Sheet and put them in a separate .tpw.
So that might well still explain why there is no link with #Include and #Append in the help docs.
It is very information having the outputdebugstringa working though
[716] LanguageTranslator Langu080.clw BrwCommand 06/05/2022 00:57:50 #EXTENSION(IS_MessagesToDebugViewLocal,'IS Send Messages to DebugView'),Procedure
[716] LanguageTranslator Langu080.clw BrwCommand 06/05/2022 00:57:50 #Prepare
[716] LanguageTranslator Langu080.clw BrwCommand 06/05/2022 00:57:50 #Group(%grpPrepareCodeTemplate)
[716] LanguageTranslator Langu080.clw BrwCommand 06/05/2022 00:57:50 #EndPrepare
[716] LanguageTranslator Langu080.clw BrwCommand 06/05/2022 00:57:50 #AT(%DataSection),Where(%ProcedureTemplate = 'Window'),PRIORITY(1303),Once
[716] LanguageTranslator Langu080.clw BrwCommand 06/05/2022 00:57:50 #Group(%grpDataSection)
[716] LanguageTranslator Langu080.clw BrwCommand 06/05/2022 00:57:50 #AT(%AdditionalDebugHooks),Where(%ProcedureTemplate = 'Window'),PRIORITY(4000)
[716] LanguageTranslator Langu080.clw BrwCommand 06/05/2022 00:57:50 #Group(%grpAdditionalDebugHooks)
[716] LanguageTranslator Langu080.clw BrwCommand 06/05/2022 00:57:50 #AT(%ProcedureRoutines),Where(%ProcedureTemplate = 'Window')
[716] LanguageTranslator Langu080.clw BrwCommand 06/05/2022 00:57:50 #Group(%grpLocalProcedureCode)
[716] LanguageTranslator Langu080.clw BrwCommand 06/05/2022 00:57:50 #AT(%LocalDataAfterClasses),Where(%ProcedureTemplate = 'Window')
[716] LanguageTranslator Langu080.clw BrwCommand 06/05/2022 00:57:50 #Group(%grpLocalProcedureMap)
[716] LanguageTranslator LanguageTranslator.clw BrwCommand 06/05/2022 00:57:51 #AT(%BeforeInitializingGlobalObjects),PRIORITY(1),Once
[716] LanguageTranslator LanguageTranslator.clw BrwCommand 06/05/2022 00:57:51 #Group(%grpBeforeInitializingGlobalObjects)
[716] LanguageTranslator LanguageTranslator.clw BrwCommand 06/05/2022 00:57:51 #Group(%grpDebugViewImageName)
[716] LanguageTranslator LanguageTranslator.clw BrwCommand 06/05/2022 00:57:51 #Group(%grpDbgVwCommandSwitches)
[716] LanguageTranslator LanguageTranslator.clw BrwCommand 06/05/2022 00:57:51 #Group(%grpMakeDebugLogFolder)
[716] LanguageTranslator LanguageTranslator.clw BrwCommand 06/05/2022 00:57:51 #Group(%grpProgramStart)
[716] LanguageTranslator LanguageTranslator.clw BrwCommand 06/05/2022 00:57:51 #At(%AfterKillingGlobalObjects),Last,Once
[716] LanguageTranslator LanguageTranslator.clw BrwCommand 06/05/2022 00:57:51 #Group(%grpGlobalProcedureCode)
[716] LanguageTranslator LanguageTranslator.clw BrwCommand 06/05/2022 00:57:51 #AT(%GlobalMap),Once
[716] LanguageTranslator LanguageTranslator.clw BrwCommand 06/05/2022 00:57:51 #Group(%grpGlobalMapEmbed)
[716] LanguageTranslator LanguageTranslator.clw BrwCommand 06/05/2022 00:57:51 #IF(%SleepDelay[100] > 0 and %SleepDelayModule[1] = %True)
[716] LanguageTranslator LanguageTranslator.clw BrwCommand 06/05/2022 00:57:51 #Group(%grpGlobalProcedure)