No idea how to describe the symbol, which looks like a stylised eye to me. If you select a photo from the allocated image libraries and then click on the button far left under the search field with the magnifying glass, you get the image in full size and can scroll forwards and backwards with the cursor buttons far right of the keyboard.
Correct, that is the symol. Now in V6 Beta you double click the picture to get full size but you cannot scroll forwards/backwards
Okay, I see now. I’m trying to find it in 6.0b13, not back in version 5. But, now back to 6.0b13 
First, though, I can’t double-click an image to see it full size. Double-clicking does nothing for me. BUT – if I right-click on an image in the image library and choose Quick Look from the drop-down menu OR just type Command-Y, I can scroll BACK through the images one at a time by pressing either the Left Arrow or the Up Arrow, and I can go FORWARD by clicking the Right Arrow or the Down Arrow.
Is THAT what you’re trying to achieve?
The “eye” symbol has been eliminated, but the same functionality is still there – I’m guessing by clicking on the “eye” in version 5 it was just a shortcut to get into Quick Look.
Thank you Stan, right-click and cmd-Y does the same like “eye” symbol in previous versions 
I was using the eye icon (Cmd Y yes) on the actual slideshow. In v5 this works:
But in v6b it produces only this:
Looks like a bug
Hmmm??? Not quite a bug. IT WORKS FOR ME! I clicked on a layer in the Storyboard and first tried a Right-Click which reveals a drop-down menu which includes File > Get Info Cmd-I AND File > Quick Look Cmd-Y. Selecting each of those by a mouse click OR pressing the required key combinations results in the correct display.
In fact, IF a single layer is selected (highlighted) and I do a Cmd-Y for a Quick Look, clicking any OTHER layer in the Storyboard reveals a Quick Look of THAT layer. Doing a Right Arrow or Left Arrow does NOT advance the selection, only the play head, so that doesn’t work.
I’ve already sent in a bug report regarding the Get Info command, though. If you do a Cmd-I, you’ll get the file info for the selected layer – BUT if you click on any other layer, the Get Info stays focused on the FIRST layer that you asked for, and not the new layer. It would be nice, if needed, that if you do a Get Info OR a Quick Look on a layer that you can move back and forth through the slideshow, click on other layers, and get the respective info UNTIL you close the displayed QL window OR the GI window. So QL seems to work, but GI does not.