Access to file services thru CMIS/FTP/SHH/Webdav/etc... protocols has no help page.
A reference and a user guide page is needed.
Source for writing help page
This source is quite helpful for Google Drive.
Hopefully the UI will be simplified by Bug 84642 and Bug 84646
*** Bug 101235 has been marked as a duplicate of this bug. ***
In recent versions, the corresponding Remote Files dialog can be invoked by File - Open Remote File or File - Save to Remote Server (or by the "Remote Files" button in the Start Centre).
Olivier Hallot committed a patch related to this issue.
It has been pushed to "master":
tdf#80652 Help file for CMIS remote servers