Typically, the application development process is more complex than that with the environment containing code repositories. Most applications comprise dozens of resources and several Lambda functions. For such applications, using Lambda console is not a good option. Also, though CloudFormation is a powerful resource, the issue is that it was built years ago, and it is optimized for infrastructure and less so for serverless.

SAM (Serverless Application Model) is an open specification (Apache 2.0) realized as a CloudFormation extension optimized for serverless. It is essentially a CloudFormation template under the covers. Hence, SAM can support anything that CloudFormation supports. You can define any CloudFormation resource within your SAM template and it will work just fine.