Currently filter offsets are absolute which is fine if the camera is fixed to the focuser permanently and there is no manual focus done. For those of us that have Moonlite or Feathertouch focusers and also those who may remove/refit their camera periodically (push-fit fitting) to perhaps change or clean filters or even refocus then inevitably the position changes. With the change in position will be a change in offset values so these would need to be reset per filter. If the filter section supported relative offsets then only one filter need have its focus position re-recorded rather than 5 or 7 etc. Obviously all the relative offsets would be against one filter.
This feature could save a lot of time refocusing.