How do I clear the previous TracBack? The menu does not have this option

Good question. On the M1, you could explicitly clear the track log. The feature was well-hidden. You had to start tracking in order to clear the log. That's not present on the M2.

I assume that you need not worry about this on the M2. Perhaps starting tracking automatically clears the log. Or maybe it places a mark in the track log at the start of the new logging session. Either way, TracBack should refer to the most recent tracking session. That is, TracBack should retrace your path from current location (the point where you engaged TracBack) to the point where the most recent tracking session started.

Thank you very much. The “last 24-hours” explains what I saw. In that span of time I activated, tested, turned off, drove 30 mi, hiked, and enabled TracBack, which pointed me back home (possibly via my trail route first?). I’ll keep this in mind. Still, a “Clear TracBack” would be a great addition. Thanks again. 

Can a Track be deleted from the Explore App which would delete it from the Mini 2 on next syncing?

Hello CowboySlim You can delete the track in explore, but you would need to also delete it off the device as well. When you sync it next it wil continue to just circle around. Syncing adds data but does not remove it from all places. To truly delete data you would need to delete it from the app, the explore website, and the device. 

If you absolutely must clear the TracBack cache, you can do so by connecting the Mini 2 to a PC/Mac via USB (make sure the USB Mode setting is on Mass Storage first), and then navigate to the /GARMIN/TempFIT/Course directory. You'll see a number of "dot files", and may see a TRACBACK.FIT file there. Example:

Delete all the files beginning with a dot (you may also delete the TRACBACK.FIT file -- it doesn't matter).

If you then select TracBack from the Navigation menu, you'll get:

Disclaimer: I am not a Garmin employee and this procedure may or may not have unexpected consequences. Use at your own risk.

Or... you could do what Leslie wrote and just wait 24 hours; the device will then clear the cache automatically. 

Even if it works, not practical in the field, which is where you need it. In any case, manually clearing anything appears to be unnecessary to use this "feature" on the M2.

I read the resources you suggested. However, I really don't think this is a helpful or expected way for the TracBack function to work.

What u/2167559 describes below is in fact what Garmin itself suggests - that is, you should test service each time before you go. Obviously that will be near my house, not the TH. Then, once in the field, being directed by TracBack to walk home because that point is within the last 24 hours is really not very helpful. There needs to be a way to clear the TracBack at the TH so I can get back to my car.

Us Back to Start instead of TracBack. Also, it is a good idea to mark your car before you set out. Then you have a waypoint to which you can navigate. This does not provide the same kind of guidance as Back to Start. But you always have a reliable location.