Installing

There are two types of add-ins that you can install.
Production Ready - These can be centrally deployed
Developer Add-ins - These are for testing

Registry - Developer Key

HKCU\Software\Microsoft\Office \ 16.0 \ WEF \ Developer 

HKCU\Software\Microsoft\Office \ 16.0 \ WEF \ Developer \ "addin GUID" 

addin GUID (String) Full path of the manifest file (C:\Shared Folder\Manifest.xml)

HKCU\Software\Microsoft\Office \ 16.0 \ WEF \ Developer \ RuntimeLogging 

RuntimeLogging - Full path of the log file (C:\Temp\LogFile.txt)

Registry - GUID Key

UseDirectDebugger - Office launches the add-in in a mode that supports direct debugging with browser developer tools.
Tools such as Visual Studio Code debugger extension or Edge WebView2 DevTools.

HKCU\Software\Microsoft\Office \ 16.0 \ WEF \ Developer \ "addin GUID" \ UseDirectDebugger 
1 = debugging enabled 
0 = normal execution (localStorage) 

UseLiveReload - Controls whether the add-in automatically reloads when source files change during development.

HKCU\Software\Microsoft\Office \ 16.0 \ WEF \ Developer \ "addin GUID" \ UseLiveReload 
1 = enabled 
0 = disabled 

UseWebDebugger - Controls the use of web debugging tools for the add-ins embedded browser / webview.
Allows the Office Web Extensions Framework (WEF) to expose the runtime context to web-based debugging protocols rather than the native desktop IDE hooks.

HKCU\Software\Microsoft\Office \ 16.0 \ WEF \ Developer \ "addin GUID" \ UseWebDebugger 
1 = enabled 
0 = disabled 

Win32WebView2 - Forces the add-in to use the Edge WebView2 runtime

HKCU\Software\Microsoft\Office \ 16.0 \ WEF \ Developer \ "addin GUID" \ Win32WebView2 
1 = enabled 
0 = disabled 

Windows Folder - Wef Subfolders

folder - C:\Users\"username"\AppData\Local\Microsoft\Office\16.0\Wef\ 

AddinInfo - aggregated info about all installed add-ins
AggregatedCache - shared cache for all add-ins
AppCommands - ribbon and app command definitions
CustomFunctions - excel custom function definitions
MetaOS - Office UI metadata and OS data
Resources - shared resources across add-ins
webview2 - webview2 runtime components (used by newer add-ins)
{GUID} - the unique GUID for an installed add-in

Add-in Package Subfolders

When an add-in is deployed using a shared folder all the resources are extracted
ExtendedManifest - extended manifest metadata
ExtendedManifestResources - resources for extended manifest
Html - the taskpane and dialog HTML files
Javascript - compiled javascript / typescript code
Manifests - the manifest.xml file
Metadata - add-in metadata
TaosAcquisition - telemetry / diagnostics data
WellKnownResources - standard resources