Suppose I have a GPX track file and I put it in the Etrex 20
The little line comes up on the screen if I select it in "track manager" and then "view""
And the Etrex "thinks" that it is "navigating" with this line, as it appears in the "where to" section
No, this isn't quite right.
Firstly, in Track Manager there's a difference betweeen 'View' and 'Show on Map'. Generally, you want 'Show on Map'. (And while you're there, choose a bright colour such as green.) This simply overlays the Track on your 'live' map as a highlight - just like a paper map and a marker pen.
You can set as many tracks as you wish, to 'Show on Map', simultaneously - this is good for marking options where you might want to make a choice when you get there.
(NB 'View' Track is just a preview - you shouldn't be in this mode while travelling, because the screen doesn't scroll with your position.)
Secondly, in this mode the GPS is
not 'navigating'. It is just dumbly showing you where you are (and if that coincides with the overlaid Track, well and good). It is perfectly usable in this mode, but navigation is better.
To 'Navigate' a Track you should use the
Where To? menu. In 'Where To?' and submenu Tracks you will find your Tracks listed, select the one you want (hopefully you gave it a sensible name) and now you will get a thick purple line indicating that you are 'navigating'.
I recommend your Routing setup Guidance should be set to
Prompted (not 'on road' as suggested above). You then choose 'On Road for Distance' when the prompt appears.
When 'Navigating' the GPS will recognise any Waypoints on or near the Track. I'm not sure about tones working - maybe they don't - but what I do is set up the map screen like this:
this is an E30 navigating a Track
ie two data fields, one showing the waypoint name, and the other showing the distance countdown, in this case warning me that I'll be taking a Right turn in 2.97km.
'Navigating' a Track in this way works very well on the Etrex 20/30