No, the Shell does not have an ARexx port.
I put some thought into it some years ago, but there are three components involved: the Shell (Kickstart/shell.kmod), the I/O handler (console handler, Kickstart/con-handler) and the display (console device, Kickstart/console.device). Only the console device has a menu and that serves only to control the console window.
What do you want to do with the ARexx port? If you just want to write stuff to the screen, you would probably want to add commands upstream of the con-handler, where the interface is a CON: device.
If you want to change the look or configuration of the console window, then you would still need to add commands upstream of the con-handler, so that it is aware of the changes to its output device. I guess that this is what you want to do, by creating new console tabs in an existing window. For that, you need a new CON: instance, and only the Shell or the built-in "Execute" command can do that (Execute "NewShell CON://..
Lastly, if you want to issue shell commands, then you need to interface at the user input level - you may as well use the built-in "Execute" command to do that for you, too.