Sorting different displaysets from same series as one displayset

as always - thanks for OHIF - an amazing project

our question:
sopclasshandlermodule creates different displaysets for different SOPClassUIDs (in our case ultrasound image and ultrasound multiframe image) from the same series
sopclasshandlermodule then sorts each displayset by instance number

instead of sorting these separate displaysets, how can we sort both displaysets as a single displayset by instance number