Did you try my first suggestion? So you have a state add the element. That seemed to work for me, though I only tested it quickly (adding element 2 fire in the example).
<JS Pre-Apply as User>let name = "VisuMZ_1_BattleCore";let command = "ActSeq_Element_AddElements";let addEle = JSON.stringify([`2`]);PluginManager.callCommand(this, name, command, {"Elements:arraynum" : addEle});</JS Pre-Apply as User>