Underlying population of potential perturbers derived from PPD substructures in the SPHERE scattered-light images. For planets in the gaps between rings (circles with inner dots) and planets in cavities (circles), these values are estimated using a proportionality factor of 8 R_Hill to account for the mass that would create the observed width in the scattered-light gap (Eq. (1)). When the gap morphology in scattered light was taken into account, planet masses are taken from detailed simulations in the literature for α = 10⁻³, and are marked with an asterisk. Simulated planets creating spiral features are also included as spiral symbols (see references in the Appendix A and see also Fig. A.1). The distributions of confirmed planets in the exoplanets.eu catalogue are shown as small dots: green (radial velocity discoveries), orange (transits), and blue (imaging).