E.g. for knobs, there are already blue "partial circles" that mark the derivation from the center (or from 0).
One could also draw partiaö circles from the default value to the current position. This should be preferrably in a shiny color, such that one look suffices to tell what knobs have changed. If a knob has not been changed, it won't have a partial circle.
fundamental asked for the feature to be programmed as an overlay: "user enters mode 'default-values', upon entering mode 'default-values' all active Valuator widgets are alerted of the mode, Widgets can display additional information by either changing their own drawing routine or by creating a child widget on the overlay layer to show if they have been changed". There may be already a 'style' field in the Valuator, which could be reused.
