Diagnostic diagram used to isolate QSO candidates in the feedback phase: X-ray to optical flux ratio vs. r-Wl colours for all the 246 eFEDS sources detected in the hard band in the eFEDS sample. Red points mark sources in the selection locus for the windy QSOs at r-Wl > 4 and log X/O > 1 (upper right corner). Blue points mark all other sources. Sources with less reliable counterparts in the hard X-ray sample are marked with dotted lines. Source XID439 is marked by a large red star.