How do savings forms get enabled?

Savings forms are enabled via the parameter Application.AQS.EnableSavingsForm.

That parameter specifies whether you can create a savings form in full projects. The option appears on the Actions menu on the Document tab of a project.

Originally, savings forms were only available for full sourcing projects, not contract workspaces or contract requests. However, if your realm has the product SAP Ariba Collaborative Sourcing Pro, this allows users the ability to create savings forms in contract workspaces and contract requests.

Strategic Sourcing
Strategic Sourcing > Strategic Sourcing Parameters/Feature Toggles