After you’ve approved the model, you cannot delete stages when editing a draft. Instead, you can merge that stage with another.
Click Marketo Home and select Analytics.
Click your approved model.
Click Edit Draft.
Right-click the stage you want to merge and select Merge Stage in the menu.
Click the specific stage in the pull down.
You can re-approve the model by selecting Approve Model Draft in the Model Actions menu.
Pick None in the Merge Stage pull down to remove the leads from your model