Hey... I just figured this one out! I have wanted to do this for 20yrs! I have searched for years on how to add a comment to a query in design mode... The only thing I found was that you could add comments to the query description in the query properties in design mode - I did not like that. So, here is how you do it!!!!

Add as many extra columns as you need. For each column, add your "Comments in quotes" for the field name, uncheck the show checkbox, sort the column ascending! Wala! You uncheck it so it cannot be seen when the query is run... If you don't sort it ascending, Access will remove it (as unnecessary) when you save and close the query.

When you add your comment, access will add a name ("Expr1:"). But when you save and close... reopen in design mode, the "Expr1:" is gone!

When you switch to SQL view, the code added is like this... ORDER BY "Comments in quotes";