Q - Will the Copy to All Plans button copy the preferences from the client case I am viewing over to all of my client cases?
A - No. The Copy to All Plans button will not copy preferences from one client case to another. In fact, the software has no feature that would make changes across all of your existing client files.
This button can be used to take a set of preferences from a given plan / scenario and apply (copy) them to all of the plans / scenarios within that client case. You might use this button to ensure that all of the plans within a given client case are working from the same set of assumptions.
In Voyant the term plans = scenarios (including the base plan).
The term client = a client case / client file, which are shown on the Open Client Record dialogue.
A client file contains one or more plans, always beginning with a Base Plan.
On the Preferences screen, the Plan Preferences -- the panels to the right side of the screen -- are applied to the individual plans within the client case you are presently viewing. Scenarios inherit preferences, initially, from the Base Plan, but preferences can be changed on a per-scenario basis, if needed.
The System Preferences, to the left side of the screen, are used by the software only going forward, as the initial set of preferences when you create entirely new client cases.
The Copy to All Plans button, located at the top of the Preferences screen, copies the set of plan preferences from the plan that you are viewing at the time to all of the plans (scenarios) within the client case you are working in.
About Preferences - A master list of the software's default assumptions and settings
System Preferences vs. Plan Preferences