r − i versus i − z colour-distribution-simulated magnitude sources from the combined catalogue in the COSMOS2020 field used to optimise the selection of companions to W2246–0526 in the redshift range 4.601 ± 0.1. Symbols are defined in the same way as described in detail in Figure 4. The figure also shows the selection function adopted by 2023Zewdie based on modified selection criteria of Ouchi et al. (2004, cyan) and the Yoshida et al. (2006, black; See 2023Zewdie for details). The grey line is the colour–redshift track of the LBG composite spectrum of Shapley et al. (2003) with the IGM absorption of Madau (1995) shifted from z = 4.0 to z = 5.5, and the symbols are the same as in Figure 4.