Mege Visible Layers into Smart Object ?

None is set up for it by default, but it is in the keyboard shortcut options so you can add your own.

But that wouldn't select all layers for you.  I was going to suggest an Action but couldn't think how to select all layers.  Dmonzon tools has scripts for Hide all Layers, and Show all layers, so it must be doable by script I'm thinking.

Or is there an existing way to select all layers?

Boy I had to do some hunting, but it does exist. ctrl-alt-a or command-option-a. Selects all layers in the layers panel. Select>All Layers

Select>Deselect layers - No shortcut listed.

Hey good find, and a bit predictable if you think about it.  I just tried and it doesn't sellect a locked BG layer, but works fine after unlocking it.

SO SB in in business and can produce an action to do what he needs.