Is there a keyboard shortcut to select the printer in Mac printer dialog boxes?
Add a new shortcut to System Prefences > Keyboard > Shortcut > App Shortcuts.

Choose an existing printer name (in my example Lexa - a Lexmark printer, a Kyocera is my default printer) and enter a shortcut:



To print with this (obviously non-default) printer enter cmdP, and once the Print dialog displays, enter altcmdP to switch to the other printer:



To print with your default printer just use the common cmdP.