UR44 is audio interface
UR 44 Main L/R output to monitor speaker

Moxf8 to computer via USB
Moxf8 is also connected L analog output to UR44 Input 3 via stereo cable
and R analog output to UR44 Input 4 via stereo cable

Do not use “stereo cables”... this is incorrect and will cause problems. Use two (2) standard TS (Tip-Sleeve) Signal cables.

I want to record both Audio and Midi from Moxf8.

The MOXF has its own built-in Audio and MIDI Interface via USB. Of course, you do not have to use it. If you prefer to use the UR44 (which can support higher Sample rates) that is your prerogative and is also a viable way to work.

But make sure you use two standard signal cables to connect the Left and Right Output of the MOXF to the UR44.
Download and install the “Yamaha Steinberg USB Driver”, this will handle Audio and MIDI from the UR44. It will also handle USB-MIDI for the MOXF.

Connect the MOXF’s USB “TO HOST” port to an available port on your computer... for MIDI communication.
Alternatively, you could use standard 5-pin MIDI cables connecting via the 5-pin ports on the UR44.
Either connection method will work...
If you connect the MOXF to the computer with a USB cable, set the MOXF MIDI I/O = USB
If you connect the MOXF via the 5-pin MIDI Ports of the UR44, set the MOXF MIDI I/O = MIDI

Sorry, I cannot help you with the Nektar T6 - because we don’t know it.
... but if it can connect via USB for MIDI do so, if it cannot, then use standard 5-pin to connect it via the 5-pin Ports on the UR44.

It matters not whether MIDI is via USB direct to the computer, or via standard 5-pin MIDI cables. Just as long as you set each appropriately for the connection you are using.

In Cubase, Setup the Steinberg UR44 as your VST AUDIO SYSTEM
Go to STUDIO > STUDIO SETUP... > VST AUDIO SYSTEM > select UR44 (Yamaha Steinberg USB ASIO)

Setup your MIDI
Go to STUDIO > STUDIO SETUP... > MIDI > MIDI PORT SETUP > here you will select which devices you want to use to enter MIDI data to Cubase MIDI Tracks. In the column labeled “In ‘All MIDI Inputs’”, place a Mark next to the Port or Ports you are sending MIDI data into a MIDI Track.

If you have selected to use the USB-MIDI connection for the MOXF, then place a mark next to MOXF8 Port 1
If you have selected to use the MIDI Ports on the UR44, place a mark next to the Steinberg UR44.

Only mark the Ports you are using.

If you use the Nektar as a MIDI Input device via USB follow instructions for the Port options for that device
If the Nektar is connected for MIDI via the UR44, place a mark next to the Steinberg UR44.