The Savings Growth Rate, found in Preferences, is used as the default interest rate (Growth Rate) for cash accounts, which are found on the Savings screen. This default interest rate is used provided that the "Use 100% Cash Asset Allocation" option is not selected for the account.
Note: On the left side of the Preferences screen are the System Preferences, which serve only as a template set of assumptions. When you create a new client case, a copy of the System Preferences will be written into your new client's Plan Preferences, which are shown to the right side of the Preferences screen. The Plan Preferences are the assumptions actually being used in the plan/scenario that you are viewing at the moment.
Importantly, this preference sets the initial default interest rate for the software's defuault cash accounts (e.g. John's Cash). These accounts act as a holding place for ready cash from future lump sum inflows and in some cases, surplus unallocated income that is not scheduled to be deposited to a specific account.
If the "Use 100% Cash Asset Allocation" option is selected, an asset allocation a 100% Cash Allocation will be used to derive a growth rate from the software's market assumptions.
The default interest rate is taken from Plan Preferences, but this default can be easily overridden for any account individually. To change the interest rate for an particular cash account, select the account on the Savings screen and in Advanced Settings > Growth, edit the Growth Rate %.
Plan Preferences vs. System Preferences
Changes to this setting on the mirror Default Inflation / Growth Rates panel in System Preferences, on the left side of the screen, will be used only going forward, as you create new client cases. System Preferences are used as a template only for new client cases. Changes to System Preferences will not retroactively affect your existing client cases.
If you want to change this preference in any existing client cases, you will need to open and edit them individually, in each case's Plan Preferences.