CTRL-SHIFT-ALT-E to do it.
Yes using a keyboard Alt key will dismiss menu list. If you do not want to click on an menu item to use it and you start to use a shortcut key combination with alt why should Photoshop continue to display a menu you opened. If you want the use the layer menu item click on it or don't open the leyere menu an just use its shortcut ctrl+shift+E.
The short cut key your use has a completely different function. It may do nothing for example the current target layer is not visible its been turned off, it may stamp the current document composite image view the visible layer into the currently empty target layer to be compatible with old Photoshop actions. or It may add a new layer above the currently targeted layer that is not empty and stamp the current composite view into it. In an action you often do not know what is current targeted. So in actions I always use SHIFT+ALT+CTRL+N SHIFT+ALT+CTRL+E SHIFT+CTRL+] This sequence of shortcuts will always add a new empty layer above the current target and become the Photoshop Target the the target will be stamped with the visible layers and that layer will be movet to the top of the layer stack. The Action now know what Photoshop target is it a stamped visible laters layer on the top of the layers stack.e
The above is a screen shot from Photshop Online Help on "Default Keyboard Shortcuts".
Jeff Schewe, Bruce Fraser, Photoshop Help all say to ALT-click on "Merge Visible" command from the layers menu to achieve the above. My confusion is: When one opens the Layers pop-up or drop-down menu and then presses ALT in anticipation of clicking on "Merge Visible" the menu disappears because the ALT key has been pressed. Just as you said. Am I reading the instructions for an old version of CS that no longer apply to current CS versions? ALT is used to open and close menus since WIndows 95 as far as I can remember. I have an alternative with CTRL-SHIFT-ALT-E but I cannot understand the instruction to ALT-Click on "Merge Visible" command in the pop-up menu. It isn;t working for me. Thanks for the help.
Yes Photoshop behavior changes over time perhaps at one time Photoshop actually worked like the documentation is written.
At one time the was no automatic new layer added when you stamped visible layers you had to add an empty layer first. So Actions were recorded that way, If Shift+Ctrl+Alt+E always added a new layer when the old action are played you would wind up with an extra empty layer. So if the current target is an empty layer the shortcut add no layer and the empty layer is stamped.
I just checked CS2, CS6, CC and CC 2014 the all work the way you wrote not the way the Adobe documentation states. Photoshop Documentation is not the best. When Photoshop operation changes need changes to documentation and actions does not get done so some sample actions don't work correctly and reported bugs go un-fixed release after release.
Photoshop releases are not always backwards compatible with prior versions of Photoshop. You have to work around these problems.