I think the manual update button should always be visible in order to easily force a rule update regardless of the automatic update setting. Along with checking the Logs->SystemLog->IntrusionPrevention it allows better troubleshooting just from the WUI.
The toggle is at Lines 936-937 in /cgi-bin/ids.cgi
# Show the “Update Ruleset”-Button only if a ruleset has been downloaded yet and automatic updates are disabled.
-if ((%idsrules) && ($rulessettings{‘AUTOUPDATE_INTERVAL’} eq “off”)) {
+if ((%idsrules) ) {