Re: M-s <left> is undefined.

[Diego Zamboni]

M-S-LEFT (org-table-delete-column)
Kill the current column.

But the keystroke combination doesn't work as expected, instead it
triggers the following info in the bottom minibuffer:
M-s <left> is undefined.

Which keys, exactly, are you pressing?

M-S-Left in Emacs Key Notation (https://www.emacswiki.org/emacs/EmacsKeyNotation) refers to Meta-Shift-Left, which in my testing works as expected, but the message you see, as posted, corresponds to what happens when you press Meta-s (the letter S) followed by "Left".

Best,

--Diego