After much trial and error, I landed on this. The prior replies helped but I needed a slight modification:
iPhone app bundle ID: com.myname.myapp
Watch app bundle ID: com.myname.myapp.watchkitapp
Watch extension bundle ID: com.myname.myapp.watchkitextension
In WatchOS Info.plist
<key>WKCompanionAppBundleIdentifier</key>
<string>com.myname.myapp</string>
In watcOS Extension Info.plist
<key>NSExtension</key>
<dict>
<key>NSExtensionAttributes</key>
<dict>
<key>WKAppBundleIdentifier</key>
<string>com.myname.myapp.watchkitapp</string>
...
</dict>
rusty-coder
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