No, they're saved on the SD card. Then in the Find menu of the GPS, instead of finding "Geocaches", you find "Custom POI" - and the option to find Custom POI doesn't appear on the GPS until you have some to find.
To clarify, what I was doing in GSAK was running this macro:
http://gsak.net/board/index.php?showtopic=...amp;#entry18194
with these icons:
http://www.thepropers.com/geocaching/60Ser...stomSymbols.htm
so that all 3,987 caches I had loaded in GSAK (from 11 PQs that I run on different weekdays) would be available on my Garmin Vista HCx, and I could see on the map what kind of cache was nearby - wherever I'm travelling in my province, and a couple other cities I'm visiting soon.
I took this Custom POI system out for a test drive today - I was prepared to be disappointed that you couldn't use the new 'geocaching mode' on the Vista with Custom POIs. <i>But,</i> it turns out you can - sort of. Once you arrive at your Custom POI (so, GC14DCX or whatever - don't forget to sign the logbook!), you can Save it, and then declare that you Found it (there's a Found button for your waypoint), and it'll automatically change the icon from whatever your custom one was (I only found traditional caches today, not sure if this will work with multi/puzzle/events) to the Geocache Found (open treasure chest) icon. Then, just like in geocaching mode, my GPS saves the cache in my calendar.
The sky's the limit for us Mac-types, I'd say. Just have to get a couple of features into the already terrific software.