apt-key says deprecated, but not saying what else to use

[Marco Möller <talby@debianlists.mobilxpress.net>]

Hello,
Command apt-key and its man page say that apt-key is deprecated, but do 
not suggest an instead recommended tool. It is only mentioned that keys 
would now be organized in /etc/apt/trusted.gpg.d/  . But how should I 
manage the keys saved there, for instance how to update them, or what 
tool of the Debian distribution is managing them there for the apt 
functionality of the Debian OS?
Guiding me to a properly up-to-date documentation about this topic would 
be welcome!
Marco.