In Hotmail, I can directly edit the html codes during composing an email. However, in Gmail, I cannot have this feature.
Moreover, Gmail does not have the built-in function to compose a table.
Recently, I accidentally find that the copy-and-paste feature in the Gmail preserves the formatting. So following the track, I find I can actually create a table simply by copy-and-paste an empty table from another editor (like Word)!
Though I cannot do further formatting (like column width adjustment), I find I already overcome one of the greatest deficiencies.