?
When you zoom in on the map, it always zooms to wherever the pointer was on the screen. So if that happens to be in a place where the Track isn't, then you'll lose sight of the Track.
Step One is to colour the Track - just makes everything so much easier. [edit: cross-post]
[edit again] Oh, and on the Etrex, Tracks show by default, but you have to 'load' a Route (in the Routes menu) in order to see it. (As well, maybe.)
On the Dakota, there is a 'show on map' option somewhere in Track Manager - but it's not the default, unlike the Etrexes where it is. With 'show on map' enabled you can have as many Tracks as you like (within limits) onscreen at the same time as ONE Route.