Log forwarding is not working on manually created log groups

[sema4-fgulmammadli]

I have this configuration in my serverless,yaml:

provider:
  name: aws
  runtime: nodejs14.x

plugins:
  - serverless-log-forwarding

custom:
  logForwarding:
    destinationARN: <arn to lambda>

resources:
  Resources:
    MyCustomLogGroup:
      Type: AWS::Logs::LogGroup
      Properties:
        LogGroupName: MyCustomLogGroup
        RetentionInDays: 90

I can succesfully deploy this to aws but I cant see the lambda in subscription filter of log group.
Does the plugin work only on automatically created log groups from functions?