Yes, you can use a Save to Repository step in the Forms process. In that step, you can decide which forms or attachments you want to save into your repository and define a folder path on where to save them using variables. If the folder path doesn't exist, it will create it for you. 

If you just want to create a folder without saving anything inside it, you will have to use a workflow service task to kick off a workflow, then have workflow create the folder.