Although there is $home\HelpViewer.exe and $home\HelpCfg.ini on my system (w7 x64, FM-18.104.22.1680) - the Help function does not work. Neither F1 nor selecting from the menu does anything.
Double clicking HelpViewer.exe correctly opens the online-help for FM-14 aka 2017.
Command Help in cmds.cfg is the same since years:
<Label Help Topics...>
<Description Open Help...>
Yes, there are some plug-ins and ExtendScripts, but as far as I see they do not manipulate the menu.
If I recall correctly there was an issue with HelpViewer.exe at the early versions of FM-14. Hence I had a copy of HelpViewer.exe from Fm-13 in use - but for the current release (build 500) the HelpViewer is OK.