Currently Edit > Select/Deselect All commands are separate:
I’d like to suggest merging them into a single command that toggles Select/Deselect All with Command-A and Option-Command-A (like Finder) shortcuts. Or, retain Shift-Command-A for Deselect All. I didn’t spot any command currently using Option-Command-A but with so many commands/shortcuts it would be easy to miss. Or, if in use give that command Shift-Command-A so Option-Command-A can be used for Deselect All.
Apple’s Mac OS X keyboard shortcuts article mentions Option-Command-A as the shortcut to deselect all items in Finder but not other apps.
Maybe the iTunes command/shortcut is Carbon app legacy?
Pretty sure I had an example or two when originally posting but haven’t found any now. I wouldn’t mind if the command was removed from DT, freeing its Shift-Command-A shortcut for other usage.