Yaml not well formed error when trying to create cross stack reference-CodePudding

I am trying to create a cross stack reference. Think of the stack that I am referencing from as the main VPC and the stack that I am creating now is basically creating a subnet in the main VPC and then sharing it with another account (VPC/resource sharing). When I validate this template in aws designer I get the Yaml not well formed error on line 15 which is:
CidrBlock: !Select [ 0, !Cidr [!ImportValue 'Fn::Sub': '${NetworkStackParameter}-VPCCIDR', 3, 8]] I am new to coding and cloud formation so I appreciate any help. Please see template below:

    AWSTemplateFormatVersion: "2010-09-09"
#Description:

Parameters:
  NetworkStackParameter:
      Type: String

Resources:
#Create Private Subnet ABC
  PrivateSubnetABC:
    Type: AWS::EC2::Subnet
    Properties:
      CidrBlock: !Select [ 0, !Cidr [!ImportValue
        'Fn::Sub': '${NetworkStackParameter}-VPCCIDR', 3, 8]]
      VpcId: !ImportValue 
        'Fn::Sub': '${NetworkStackParameter}-VPCID'
      AvailabilityZone: "us-east-1a"
      Tags:
        - Key: "name"
          Value: "PrivateSubnetABC"

#Create Resource Share
  PrivateSubnetABCShare:
    Type: AWS::RAM::ResourceShare
    Properties:
  #    AllowExternalPrincipals: Boolean
      Name: "Service ABC"
  #    PermissionArns:
  #      - String
      Principals:
        - "1234567890"
      ResourceArns:
        - !Sub 'arn:aws:ec2:${AWS::Region}:${AWS::AccountId}:subnet/${PrivateSubnetABC}'
  #    Tags:
  #      - Tag

CodePudding user response：

In that case, its much easier to write it as individual blocks, rather then trying to do it in one line:

Resources:
#Create Private Subnet ABC
  PrivateSubnetABC:
    Type: AWS::EC2::Subnet
    Properties:
      CidrBlock: !Select
         - 0
         - !Cidr
            - !ImportValue
                'Fn::Sub': '${NetworkStackParameter}-VPCCIDR'
            - 3
            - 8
      VpcId: !ImportValue
        'Fn::Sub': '${NetworkStackParameter}-VPCID'
      AvailabilityZone: "us-east-1a"
      Tags:
        - Key: "name"
          Value: "PrivateSubnetABC"