public final ObjectProperty<Callback<Workbench, Tab>> tabFactoryProperty() {
        return tabFactory;
    }
Returns a map of all overlays, which have previously been opened, with their corresponding
model object {@link WorkbenchOverlay}.

@return a map of all overlays, which have previously been opened, with their corresponding
model object {@link WorkbenchOverlay}.
workbenchfx-core/src/main/java/com/dlsc/workbenchfx/Workbench.java