Some info about collections that you might have missed:
XT2-P330
Note that some of the Zumo screens will scroll so that you can see all of the options available.
Routes, tracks, waypoints - the same items can be added to more than one collection if you wish. They do not necessarily ‘belong’ to a single collection.
Collections are not defined in gpx files. The Zumo has a lot of tools to make adding multiple items to a single collection, and removing items from collections. Unlike the XT1, the XT2 and XT3 (?) can be used to create and name collections. Seems logical, but surprisingly, the XT1 did not allow you to create a collection. You can create collection on the explore.garmin.com site, and on your phone - but that requires Tread/Drive to be set up to sync.
As shown in the notes in the link - one way is to import new data into one collection, and then move it to other collections.
Or when importing, select the items that you want to place into a collection, and none of the others. Then do the same for a second collection.
It is worth spending the time as you can then turn on visibility for just one day of a multiday trip.
Waypoints are imported automatically if they are placed in internal storage, so that complicates things a bit.
Note that ‘saved’ and ‘favourites’ which had been the terms used for ‘Waypoints’ on everything up to the XT1, were changed (at last ) to ‘waypoints’ on the XT2. I assume that ‘waypoints’ is also the term that is used on the XT3. So the ‘saved’ referred to in a comment above is not the term that was synonymous with ‘favourites’ !
One last thing. If you have screen capture enabled, the icon on the XT2 is located top right of a landscape screen. It masks almost completely, one of the buttons on the green banner ‘collections’ screen which makes it impossible to carry out one task - to open the 3 dot menu giving access to other commands. You have to turn the screen portrait to gain access to it - or file your finger nail to a very fine point, then turn it back again. My guess is that they have not fixed this for the XT3.