You can just use the script mentioned by ShadowPierce.
If you only want to have a skill for taunting the enemies, it could look like this:
In the header you can use a neg. value for threat-increase and a pos. value for defense-decrease, so that whatever you do the threat will decrease. Set the display to false to just untoggle the threat-window. No you add a skill that makes exactly what you want and define how many turns it will be active. In this example, skill 1 increases the threat of the actor by 6 and decreases the threat of everyone else by any value of choice (if you set it to zero, 2 or more actors can threat the enemies at time). Now when performing the skill, all enemies will attack the actor and with every turn the threat will decrease ==> after 6 turns of normal attack, the threat will be down to zero again. When you, after 2 turns, decide that the threat should be gone , you can start to defend, decreasing the threat now by 2 (or whatever you define).
ATTACK_THREAT = -1 # Threat to increase when actor attacks
DEFEND_THREAT = 2 # Threat to decrease when actor defends
THREAT_CHANCE = 100 # The chance of enemies attacking based on threat
THREAT_DISPLAY = false # Display player's threat besides their name
THREAT_WINDOW = [480, 64, 160] # Whether to enable or disable threat window
#========================================================================
# SKILL THREAT CONFIG BEGIN
#========================================================================
when 1 then [6, -1000] # Cross Cut