Is there any way I can add triggers to a lambda function in Terraform?

I know that we can add an event source mapping, but that is not what I am looking

Event source mapping for SQS, DynamoDB and Kinesis is exactly what you are looking. What you are showing on the screenshot is just AWS Console representation of the Event source mapping for the 3 services.

You can configure directly in your terraform code the subscription to events from a lot of resources and integrate with multiple notifiers in AWS. This is example to add a trigger to a lambda based in a subscription event from SNS.

data "aws_autoscaling_groups" "groups_servers" {
  depends_on = [
    aws_autoscaling_group.servers_cluster_asg_masters,
    aws_autoscaling_group.servers_cluster_asg_slaves
  ]
  filter {
    name   = "auto-scaling-group"
    values = "servers-masters-nodes"
  }
  filter {
    name   = "auto-scaling-group"
    values = "servers-slave-nodes"
  }
}

resource "aws_sns_topic" "sns_servers" {
  name = "sns_servers"
}

resource "aws_autoscaling_notification" "new_instances_notifications_servers" {
  group_names = data.aws_autoscaling_groups.groups_servers.names
  notifications = [
    "autoscaling:EC2_INSTANCE_LAUNCH"
  ]
  topic_arn = aws_sns_topic.sns_servers.arn
}

resource "aws_sns_topic_subscription" "sns_servers_servers_subscription" {
  depends_on = [
    aws_lambda_function.servers-cluster-orchestator
  ]
  topic_arn = aws_sns_topic.sns_servers.arn
  protocol  = "lambda"
  endpoint  = aws_lambda_function.servers-cluster-orchestator.arn
}

resource "aws_lambda_permission" "sns_permission_servers" {
  depends_on = [
    aws_lambda_function.servers-cluster-orchestator,
  ]
  statement_id  = "AllowExecutionFromSNS"
  action        = "lambda:InvokeFunction"
  function_name = aws_lambda_function.servers-cluster-orchestator.function_name
  principal     = "sns.amazonaws.com"
  source_arn    = var.sns_servers_topic
}

resource "aws_lambda_function" "servers-cluster-orchestator" {
  s3_bucket     = "my-bucket"
  s3_key        = "my-lambda.zip"
  function_name = "my-lambda"
  role          = aws_iam_role.iam_for_lambda_servers_cluster.arn
  handler       = "lambda_function.lambda_handler"
  runtime       = "python3.7"
  timeout       = "60"
}