Why? Is there any other key for them? Just curious (don't suggest to make custom actions as I was told on facebook, lol; actually I don't need this at all, just explore PS features)
This won't do what you are asking, but it could speed things up. Having created the adjustment layer, hold down Command/Control and tap the left square bracket key ( [ ). This is the keyboard shortcut to move a layer down one level within the layer stack.
What would happen if there was a single backgroundLayet?
What would happen if there was a single pixel layer?
An adjustment layer logically has to be above a layer to adjust it.
yep, but a file can have many layers and masks!
besides, it may be useful for creating clipping layers (as mentioned in the comment BELOW, lol 🙂
Yes a file may or may not have many layers.
Why is there no modifier key? Only Adobe knows.
The lowest common denominator is a flattened image, which can't have anything below the Backround layer. Therefore by default an adjustment layer has to go above.
I'm not saying that such a feature has no merit, I'm just stating why it only does what it does and why I think it works that way.
P.S. the modifier key works directly on an icon, however adjustment layers are selected from a drop down list, perhaps that also affect key modifiers.
I have thought about this in the past when clipping an adjustment layer. If you add another adjustment layer it is not clipped, so I was wondering if it was possible to add the new adjusment layer beneath the current one, and that would keep both adjustment layers clipped? Pure lazyness, but we are forever looking for ways to save a keystroke or two.
that's a good example why we need this!
If you inserted a new layer or adjustment layer inbetween the clipped layer and the base layer it would automatically inherit the clipping. Even if the adjustment layer is added above the clipping group and it is therefore not clipped, moving it into the clipping group structure would also make it clipped. So an action or script could help with this workflow, otherwise this is not really the place to put forward feature requests if you wan't Adobe to consider them.
"Is there any other key for them?"
I do not think so, it would be nice to learn new shortcut.