Blizz threat meter working

There is no menu to configure it. Your % of threat is an event displayed in your floating combat text messages. The mouseover tooltips are displaying your current % of threat. The Threat Meter shows either the mob is attacking you (indicating in the SCT), if you are High on the mob aggro table (indicated by yellow or red dots in the tool tip). The threat meter has its own table indicating the TPS and the threat gain. It can be accessed through:

/console showThreatMeter 1
/script function IsThreatWarningEnabled() return 1; end