Sometimes catalogers want Concise MARC 21 LOC manual, while cataloging on any framework, so the "?" help link point to http://www.loc.gov/marc/bibliographic/concise/bd100.html instead of http://www.loc.gov/marc/bibliographic/bd100.html.
To solve this, I propose a syspref to switch between Hide/Show Full manual/Show Concise manual, something like DocumentationOnMARCeditor.
On a second step, is useful to select between languages, but AFAIK LOC doesn't give a good support or API (PDF only for Spanish or German, for eg).
Related bug: #5546 - Ability to hide MARC documentation links.
Fixed by bug 11674 and bug 20785