For advanced users, CalTopo offers a number of custom layers: MapBuilder, viewsheds, sunlight, scanned maps, DEM-based shading and third-party WMS and tile sources.  A persistent issue with these layers is that they are tied to either the map you are working on, or the URL of a blank page.  It’s easy to go wild customizing them, and then suddenly find yourself starting from scratch with a new map.

In a long overdue solution, you can now save custom layers to your account.  Every custom layer dialog has a “Save To Account” link at the bottom which adds that layer to your account:

As with maps, these layers are listed on a tab on the account dialog:

And shown in a separate section of either the layer dropdown or the overlay list, depending on how the layer is configured:

Additionally, for subscribers, these layers will show up in your KML SuperOverlay File, or for pro users, WMS or WMTS Service:

A viewshed overlay in Earth

Sunlight analysis viewed in Earth