Adding Custom Navigation Buttons to Locked Redwood Procurement Pages

I am working with a Redwood Procurement page in Visual Builder Studio (VBS). My requirement is to add three custom buttons to the header toolbar to facilitate navigation to related application areas (Suppliers, Process Requisitions, and Purchasing).

However, because this is a standard Redwood page, many UI components in the Page Designer are "greyscaled" or locked, preventing the drag-and-drop addition of new buttons into the header toolbar. Since the standard extensibility constants do not provide a slot for these specific actions, how can I inject custom navigation elements into the existing Redwood header while ensuring they persist through page re-renders?