Is there a workaround to keep app settings which not defined in Bicep template?

From this article: Merge App Settings With Bicep.

1. Don't include appSettings inside the siteConfig while deploying.
2. Create a module to create/update appsettings that will merge the existing settings with new settings.

appsettings.bicep file:

param webAppName string
param appSettings object
param currentAppSettings object

resource webApp 'Microsoft.Web/sites@2022-03-01' existing = {
  name: webAppName
}

resource siteconfig 'Microsoft.Web/sites/config@2022-03-01' = {
  parent: webApp
  name: 'appsettings'
  properties: union(currentAppSettings, appSettings)
}

main.bicep:

param location string = resourceGroup().location
param webAppName string = 'thomastest-appsettings-002'

// Create an app service plan
resource plan 'Microsoft.Web/serverfarms@2023-12-01' = {
  name: '${webAppName}-asp'
  location: location
  sku: {
    name: 'F1'
  }
}

// Create the webapp without appsettings
resource webApp 'Microsoft.Web/sites@2023-12-01' = {
  name: webAppName
  location: location
  properties: {
    httpsOnly: true
    serverFarmId: plan.id
    siteConfig: {
      ftpsState: 'Disabled'
      minTlsVersion: '1.2'
      netFrameworkVersion: 'v8.0'
      metadata: [
        {
          name: 'CURRENT_STACK'
          value: 'dotnet'
        }
      ]
      // Dont include the appSettings
    }
  }
}

// Create-Update the webapp app settings.
module appSettings 'appsettings.bicep' = {
  name: '${webAppName}-appsettings'
  params: {
    webAppName: webApp.name
    // Get the current appsettings as an object
    currentAppSettings: list(resourceId('Microsoft.Web/sites/config', webApp.name, 'appsettings'), webApp.apiVersion).properties
    appSettings: {
      Foo: 'Bar'
    }
  }
}