Help button in that dialog reaches "Welcome to the LibreOffice Calc Help", to reache the appropriate Help you will have to do additional clicks 'Menus -> Tools -> Protect Document'
I think that's the Help that should be reached, because User so has an overview concerning the alternatives 'Protect Sheet' <-> 'Protect Document'
in Help 'Protecting Sheet' (what can be reached from Help 'Menus -> Tools -> Protect Document') under heading "Password (optional)" there should be a link to Help 'Password', this link currently is missing.
A fix for this one should be done together with fix for "UI: Context sensitive Help <f1> and Help Button missing in 'Tools -> Protect Document -> Document' dialog"
Tested with LO 18.104.22.168, Win 8.1
Issue 1 (Description):
TOOLS -> PROTECT DOCUMENT -> SHEET
Help button opens a currently not yet existing online help page -> Bug, help page is still missing
Issue 2 (Comment 1):
TOOLS -> PROTECT DOCUMENT -> DOCUMENT
Help button opens the corresponding online help page -> seems ok for me
Removed the blocking of bug 80430 because: 1) it is a wikihelp issue and 2) the help pages exist in localhelp
Gabor Kelemen committed a patch related to this issue.
It has been pushed to "master":
tdf#60873 Link Protect Sheet dialog to its own help page