How to interrupt focus?

lol, you could always carry a huntsman's horn with you...that is how Beagles and Foxhounds and Basset's are recalled from scent overseas. Seems to work well .

What type of tracking is it?  I don't want to give you "bad" advice b/c I'm only familiar with Schutzhund tracking, but not AKC or SAR or trailing.  What would be the reason for getting the dog's attention and turning it away from the track?

From the perspective of SchH tracking, the dog should maintain drive and focus, but not to the point of obsession and being hectic.  At that point the dog is not really thinking/problem solving, and it also tires the dog out physically and mentally much faster.  You don't want to end up with a dog that tracks like a robot for the first leg or two and then fizzles out by the end of a longer track.

As far as pausing the dog, I guess I would train a down/platz command and use that.  In SchH I'd never want to pull my dog off the track or pull his attention away from the track (assuming he was on the track and tracking correctly).  His indication is to down at an article so a "platz" command on the track would not be unreasonably or completely unexpected for him.  I would resume the same I would at an article, walk up on the dog's right, give a food reward, and command to re-start.

Actually she is searching. She tracks and air scents as needed really. It is not as critical to keep her nose on the ground, so long as she finds the person, she can do it as she pleases lol.

The only reason I would want stop or pause-- if we are on a track on leash I can stop her fine. However off lead, just in case there is ever any dangerous situation- an unknown road or mean dogs- I would like her to wait.

Our old mal would stop with a word. Greta, however, will do a great recall anywhere UNLESS she is on a track! A park full of kids or a class of dogs she listens good. If she is looking for the scent I can direct her, but once she is on it, nothing else exists. Should I leave her alone, or keep trying a recall?

I should say trailing, because she doesn't neccesarily follow each step sorry.

Again, I'm hesitant to advise because I have no idea what the protocol is for SAR trailing, but I would work on distance downs, just in general.  Don't put them on the trail yet.  Proof them in other contexts first.  I believe this command is MORE important than a recall, because sometimes the recall might be more dangerous.  Two examples I have encountered: 1) The dog has gotten across a busy street and you want to catch it, but a recall could be deadly if you call the dog and a car comes.  2) In protection work I have a dog that is not sleeve focused so the helper cannot "slip" the sleeve off his arm until I have my dog's lead and can direct him away from the helper.  One day the helper had a brain fart and slipped the sleeve while I was probably 30 yards down field and nowhere near the end of my line.  The helper instantly ducked on the other side of the blind and assumed a very submissive position so the dog did not see him there.  If I'd recalled the dog, he would have seen the helper, ignored me, and gone after him because that is what he is trained to do.  Instead I commanded him to platz/down and then ran over to him and picked up the line.  I could also imagine situations where you might be in the woods and come across a predator.  Recalling the dog to run back to you might put the predatory in prey drive/predatory mode very quickly.

If you command the dog to down away from you, then at least the dog is still on the track/trail and can re-start at the same spot.