It's already documented in prose, now add it to the synopsis too.
<cmdsynopsis>
<command>systemd-analyze</command>
<arg choice="opt" rep="repeat">OPTIONS</arg>
+ <arg choice="plain">set-log-target</arg>
+ <arg choice="plain"><replaceable>TARGET</replaceable></arg>
+ </cmdsynopsis>
+ <cmdsynopsis>
+ <command>systemd-analyze</command>
+ <arg choice="opt" rep="repeat">OPTIONS</arg>
<arg choice="plain">verify</arg>
<arg choice="opt" rep="repeat"><replaceable>FILES</replaceable></arg>
</cmdsynopsis>