by Julieanne Kost
If you need to create a flattened copy of your layers to use in an action (while leaving the underlying layers intact), while recording the action:
1) Create a new, blank layer at the top of the layer stack.
2) Use the shortcut Command + Option (Mac) / Control + Alt (Win) + Shift + E to “flatten” a copy of the layers onto the empty layer (that you just created at the top of the layer stack).
3) Although you will see “Merge Visible” as the recorded step in the action, you will also see the disclosure triangle to the left of the Merge Visible command. Click the triangle to reveal that using the shortcut to “Merge Visible” is different from using the menu item to “Merge Visible” as the shortcut merges the visible layers on the new layer that you created in step 1 (as opposed to merging the visible layers into a single flattened layer).