Issues embedding Finder Sync extension via electron-builder - swift

Question

I have an Electron application that integrates with OS X Finder via a Finder Sync extension. Overall, the application has three parts:
Electron application
Swift Application
FinderSync extension
The Electron application is the main entry point. On start up, it creates a child process that runs the Swift application. The Swift application has embedded in it, the FinderSync extension. The Swift app and FinderSync extension communicate over ICP so that the FinderSync extension can get the correct information for badges and context menus.
I build everything with electron-builder. It ends up with a structure like:
- MyElectronApp.app
- Contents
- PlugIn
- MyExtension.appex
- MacOS
- MySwiftApp.app
- Contents
- PlugIn
- MyExtension.appdex
- (All the other app contents)
When I install the application and when I run it, I see this in Console.app
rejecting; Ignoring mis-configured plugin at [/Applications/MyElectronApp.app/Contents/MacOS/mySwiftApp.app/Contents/PlugIns/myFinderExtension.appex]: plug-ins must be sandboxed
The plugin is marked as sandboxed, This is for the inner instance of the plugin. I do not get this for upper one.
When I launch the application, I can see that my plugin is running in the Finder Extensions Preference Pane. If I toggle the extension in the Preference Pane, I can see in Console.app that the extension and Swift app are communicating with each other. But I do not see my context menu or badges in Finder.
I do see this in the logs for my Swift application and Finder Extension:
LSExceptions shared instance invalidated for timeout.
The extension is Sandboxed and the Swift app is not. It took me awhile to get those entitlements "correct". I have the plugin listed twice in the Electron app. I found that if I didn't put it in the top level PlugIn directory, then it would not be registered with the OS. When I query pluginkit, I see that the first instance of the extension is running. The extension and the Swift app have the same application group so they can do IPC.
At this point, I'm not really sure what I can do. It seems that the plugin launches with the Electron app and not when I launch Swift app from within Electron.
To get to this point, I worked through code signing issues and sandbox issues. I am not using a provisioning profile. I do have a developer certificate from Apple that I use for signing.
Any help would be greatly appreciated. If there was an article where they published a Finder extension with electron-builder, that would be great as well.
Below are some other files:
electron-builder entitlements file:
...
<dict>
<key>com.apple.security.cs.allow-jit</key>
<true/>
<key>com.apple.security.cs.disable-library-validation</key>
<true/>
<key>com.apple.security.cs.allow-unsigned-executable-memory</key>
<true/>
<key>com.apple.security.automation.apple-events</key>
<true/>
<key>com.apple.security.files.user-selected.read-only</key>
<true/>
<key>com.apple.security.app-sandbox</key>
<false/>
</dict>
...
electron-build settings in package.json
"build": {
"appId": "com.myapp",
"productName": "My App",
"copyright": "Copyright © 2020 ${author}",
"files": [
"./index.js",
"./modules/**/*",
"./iconSmallTemplate.ico"
],
"extraResources": [
{
"from": "./resources/",
"to": "./",
"filter": [
"**/*"
]
}
],
"mac": {
"appId": "com.myapp.mac",
"category": "public.app-category.productivity",
"type": "development",
"identity": "Apple Development: ME (#####)",
"extraFiles": [
{
"from": "mySwiftApp.app",
"to": "MacOS/mySwiftApp.app"
},
{
"from": "myFinderExtension.appex",
"to": "PlugIns/myFinderExtension.appex"
}
]
}
}