Creating a new Quick Step allows you to add a ribbon item to perform a custom action, such as a workflow. When you create this Quick Step users can easily activate the workflow from the Ribbon. Below is a screenshot of the configured Quick Step in the ribbon:
To create this, from the Browser, select the List Ribbon and then select the Library Tab and the New Quick Step button.
From here, SharePoint Designer will open and you will be able to enter the data for the Quick Step:
You will notice that once you select ok you are redirected to the list page in SharePoint Designer and your Quick Step is listed under the Custom Action section.
Also notice the Ribbon. You will see that you have another location to create the custom actions. From this menu you can see that we can create the custom action in different locations and when you click one of those options you will see we have more options than just linking to a workflow.
When you select one of the items, you will see a similar entry screen that allows you to select the custom action you want to complete. You can navigate to a form, start a workflow or navigate to a URL.
Below are some screenshots with samples of the locations that you can add the items. I used a document library, so I don't have an example from the new item form that you would have in a list.