Can I daisychain multiple Arduino Nanos to a single USB port (specialized purpose)
For a USB topology to operate one needs a USB controller which knows about all the different USB protocols necessary to communicate with all the different USB peripherals (this is why a USB controller is usually a fully capable computer) all connected through a USB hub.  It is unlikely a USB network could be created using only peripheral USB devices which were wired directly together.

To communicate between several Arduinos and a computer it would be much easier to use a serial bus made for multiple drops like RS485. There are many RS485 to USB converters available like this one for computers that do not have an RS485 port.