Is there a command that we can use to install the various addons that were available when first installing Cyberpanel?
E.g. so we can install PowerDNS, Postfix, Pure-FTPd, Remote MySQL, Memcached, Redis or Watchdog.
I think I remember seeing that in documentation but can’t find it.
Those are not really addons and except Redis, nothing else from the list you mentioned can be installed at later stage with one click option.
The options you see while installing Cyberpanel for the first time is the Stack option along with the setup you require for your server. This cannot be changed later easily. Yes, you can definitely but that needs more knowledge in linux administration commands. You can manually install all these but you should be knowing how to configure it too.
It is better to spin up a new server with all these installed and then shift all your sites to this new server.