is there a way to add a module C between A and B by simply drag&dropping it there, and it connects automatically?

@nilsemil New in Pd 0.49....... (not a plugin).... and unsure whether it will do exactly what you want... but it might....
https://forum.pdpatchrepo.info/topic/11851/where-to-install-hotkey-p.lugin-tcl
David.