Everything to look up
What you need once a year does not have to be memorised - it has to be findable.
Morse code is more than twenty-six letters. There are digits, punctuation marks, prosigns with no equivalent in the alphabet, a system of abbreviations for on-air work, and a scale for rating signals. Most of it is not learned but looked up, and the pages below are what you look it up in.
Every list can be heard, not just read. A character you need for the first time should be heard once; the written form of dots and dashes otherwise leads straight back to counting.
Where to start
The chart is the complete overview and prints on one page. If you only want letters, the alphabet is the better place; digits have their own page with their regular pattern under numbers, and punctuation is separate because only a handful of marks ever appear on the air.
What on-air work adds
Prosigns are letter pairs run together with no gap - they do not say what is meant, they say what is happening: start, end, understood. Q codes replace whole sentences with three letters and work across languages, CW abbreviations save characters, and the RST report is the three-digit number that tells the other side how they are coming in. Ready-made wording for the whole sequence is in the CW phrasebook.
Two special cases
SOS has its own page because it is neither a word nor an abbreviation: it is one continuous pattern of nine elements with no internal letter gaps, chosen in 1906 precisely because nothing else sounds like it through noise.
American Morse code is the original 1844 version and a different language from what is used today. Anyone deciphering an old recording or a museum piece needs it; for on-air work it has been irrelevant for over a century.