Nope, this is indeed very high on the list, and it hasn't happened for the same reason the manual isn't up to date: I haven't been getting anything done for the past several years. Entirely my fault.
Having said that, if people wanted to contribute some of the missing help screens, that'd be a relatively easy way to contribute to Snap!. In the help folder inside the Snap! sources, the files BLANK.png and BLANKWIDE.png embody the common background of the help screens without any text; use them as a starting point.