In bug #83877 the Writer -> Insert -> Signature Line dialog has been added.
Let's not forget to document it before 6.1 once the actual work is finished there :).
Olivier Hallot committed a patch related to this issue.
It has been pushed to "master":
tdf#115599 Add signature line help page
Clicking Help in Writer -> Insert -> Signature Line dialog in 6.2+ doesn't invoke help page.
Is it this bug?
(In reply to Timur from comment #2)
> Clicking Help in Writer -> Insert -> Signature Line dialog in 6.2+ doesn't
> invoke help page.
> Is it this bug?
Should be a different one. The commit in comment #1 (seemingly) correctly added this line:
+ <bookmark xml-lang="en-US" branch="hid/cui/ui/signatureline/SignatureLineDialog" id="bm_id581526498170919" localize="false"/>
This should do the trick, at least in theory - so please open a new bug if it still does not work.