No need to detach audio. Just go to Inspector, select Audio, make it dual mono and deselect the track you don’t need.
And now I see you have a few posts so I recommend to get some basic training like Ripple Training.
You can copy the range and paste it to a new Project. Or make a copy of your Project and select a range and make a Compound clip of that range and save it to a Event of your choise.