Select Pixel - Keyboard shortcuts location at Photoshop layout.

As far as I know, Select Pixels (as found when right clicking a layer thumbnail) does exactly the same thing as Select All which has the the shortcut Ctrl a  As Jane has said, single letter shortcuts are used for Tools (but can be swapped between tools).   However if you do want a single key shortcut for Select All you can use one of the Function keys.  In my experience, the only time the default Function key shortcuts are useful is when using a single small screen — like on a Notebook computer — so I personaly have reasigned most of my function key shortcuts (they are far too precious not to use).

BTW  I would be interested to hear if Select Pixels  from right clicking a layer means something other than Select All

The only way that comes to my mind is to record single step Photoshop action and to assign keyboard shortcut to it.

Start recording action then perform Ctrl + click on layer thumbnail to load selection. You should see step: Set selection and when you expand it there shoukld be To transparency channel as shown on screenshot below.

Double click on the right side of action name then choose function key which is a must and one or two more modifiers Shift/Ctrl and click OK. That is is, you have assigned shortcut to play action and select pixels on currently selected layer in the Layers panel.

Hi @reliable_Harmony15A7 

Single key shortcuts are assigned to Tools and cannot be reassigned. "A" is shared by the Path Selection tool and the Direct Selection tool.

The easiest way to select the pixel on a layer is to use the built-in shortcut: hold down Command (Win: Ctrl) and click on the layer thumbnail. Will that work for you?

Go to Edit > Keyboard Shortcuts to change shortcuts. Did you choose Panel Menus from the drop down?

~ Jane