  Supermassive black hole (SMBH) feeding and feedback processes are often
considered as disjoint and studied independently at different scales, both in
observations and simulations. We encourage to adopt and unify three
physically-motivated scales for feeding and feedback (micro - meso - macro ~
mpc - kpc - Mpc), linking them in a tight multiphase self-regulated loop. We
pinpoint the key open questions related to this global SMBH unification
problem, while advocating for the extension of novel mechanisms best observed
in massive halos (such as chaotic cold accretion) down to low-mass systems. To
solve such challenges, we provide a set of recommendations that promote a
multiscale, multiwavelength, and interdisciplinary community.
