Note that this is an MCX file so does not identically follow the schema provided in your manifest.json file.
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "
http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>PayloadContent</key>
<array>
<dict>
<key>PayloadContent</key>
<dict>
<key>com.google.Chrome.extensions.iblnnhdjoilnigecdnnjlhnakihjopmb</key>
<dict>
<key>Forced</key>
<array>
<dict>
<key>mcx_preference_settings</key>
<dict>
<key>serverUrl</key>
<string>Hello World</string>
</dict>
</dict>
</array>
</dict>
</dict>
<key>PayloadEnabled</key>
<true/>
<key>PayloadIdentifier</key>
<string>0a3dd694-2aa3-4cbc-a8da-38859c620b75</string>
<key>PayloadType</key>
<string>com.apple.ManagedClient.preferences</string>
<key>PayloadUUID</key>
<string>0a3dd694-2aa3-4cbc-a8da-38859c620b75</string>
<key>PayloadVersion</key>
<integer>1</integer>
</dict>
</array>
<key>PayloadDescription</key>
<string>Example policy for server.</string>
<key>PayloadDisplayName</key>
<string>Managed Storage Example</string>
<key>PayloadIdentifier</key>
<string>extensionupdateserver</string>
<key>PayloadOrganization</key>
<string></string>
<key>PayloadRemovalDisallowed</key>
<true/>
<key>PayloadScope</key>
<string>System</string>
<key>PayloadType</key>
<string>Configuration</string>
<key>PayloadUUID</key>
<string>71feadbc-6c9a-49e9-aa6f-d3625ce8639a</string>
<key>PayloadVersion</key>
<integer>1</integer>
</dict>
</plist>