Workflow will be enabled for all the models which are newly created. The workflow by default contains Start and End activities. But ProcessInstance will not be created for Start, so you can't see the newly created items in the worktop (which will be in Start activity). So currently there is no way you can goto the list of items which are in Start activity.
Now workflow is an option for the model. So for master models, no need to define the workflow. And hence if workflow is enabled, ProcessInstance will be created during new item creation (new item can be created through browser/New Command/CsvImport). So the user can see the newly created item in the worktop. The following diagram shows how this option is going to come in Studio.
For existing models which doesn't have workflow enabled:
For the older models, if you don't want the workflow you have to delete the workflow using the button in the tool bar (see the above image). Other wise ProcessInstance will be unnecessarily created for those models also which will pollute your datastore.