So, it's almost the last place that cannot be translated. This is the first problem.
And another more major problem: in existing installations the table 'help_items' is not updating, maybe even in Major upgrades. Those users who use the helper might not know about new available keys, etc.
I propose to "move" this table directly to PHP code, as is done already for triggers function helper.
This will solve both problems and even in Minor versions users will see new available keys.
After changes, we will translate these strings
Related issue: https://support.zabbix.com/browse/ZBX-2265