The status bar of the envelope editor already shows relative panning for the pan envelope. It would be helpful to also show this in more places, for example

• Note Properties dialog, for pan effects
• Pattern editor status bar
• It would be more complex to show it in the channel properties, but I think it is in fact not necessary as there is a slider next to it.
• Default pan of samples and instruments already shows it as a tooltip. This is good enough for now, due to space contraints.