We moved your question to its own thread, as it goes in a completely different direction from the original poster’s issue.

Your question does not specify what the “external audio fx unit ” is ... so our answer cannot be specific. You also don’t mention if you are using an entry level or Pro level of DAW software. There are several ways to approach this....

Cubase Pro, for example, allows you to setup VST Routing (called “External Instrument” and “External Effect” ).
VST (Virtual Studio Technology) is a Steinberg innovation that in 1996 introduced the use of external hardware (both synthesizers and effect processors) into the Digital Audio Workstation environment. You can setup routing so that your audio can be processed within the DAW. Cubase has advanced delay compensation... which it measures and deals with...

If the effect processor is an external hardware device, you can setup to route signal to it from any of the audio inputs arriving in the DAW. Cubase allows you to set it up in a Send/Return situation available for all DAW audio Tracks.

If you don’t have the Pro version of your DAW (with advanced routing) you windup thinking about plugging outputs to inputs and standing on one foot while facing east... mostly those inventions/solutions are best figured out on your own... based on what the effect is and what you need to accomplish.

You could, for example, assign the MONTAGE instrument Part(s) you wish to process to the Analog Assignable Outputs (AsgnL/R), connect the ‘external audio fx’ to receive signal from the MONTAGE AsgnL/R — return the external fx’s audio to the MONTAGE A/D In, which can be routed on its own discreet USB Output to the DAW.

In this situation you have isolated the external hardware (Effect Return) by routing it to the A/D In and Out to the DAW on a discreet USB bus. You would work with DIRECT MONITOR OFF and use the the DAW to manipulate your monitoring choices. Totally doable.

Thanks. Yes I am using the Montage as the audio interface (I dont have another) so I want to keep everything together that way. I am referring to using an external fx pedal so i think this is the option I have to go with unless theres another way. But then I want everything captured by the DAW in the end.

"You could, for example, assign the MONTAGE instrument Part(s) you wish to process to the Analog Assignable Outputs (AsgnL/R), connect the ‘external audio fx’ to receive signal from the MONTAGE AsgnL/R — return the external fx’s audio to the MONTAGE A/D In, which can be routed on its own discreet USB Output to the DAW."