The help text for digital signatures has only instructions for Linux. Windows and macOS are missing. https://help.libreoffice.org/Common/Applying_Digital_Signatures
Code reference: http://opengrok.libreoffice.org/xref/help/source/text/shared/guide/digitalsign_send.xhp Apparently there is some instruction for Windows, it's just not visible in the Wiki. No instructions for Mac so this part is valid.
Katarina Behrens committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/help/commit/?id=d32748eb92d52f1163ff560529ac488dfb25a3b7 tdf#105606: Clarify access to X509 certificate storage
A polite ping to Katarina Behrens (CIB): is this bug fixed? if so, please close it as RESOLVED FIXED
Offline help is fixed. I've no idea about online help