I am not sure what the actions menu is, are you using some other battle plugins as well? You could try this instead, I guess it might be more compatible if another plugin customizes what the fight command does:
this.commandFight(); this.commandItem();
You cannot keep it on the party command menu because battle needs to know which actor is using the item as part of their turn, and there is no actor set on the party command window. If you want some mechanic where no actor uses the item for their turn, but it still gets used somehow, you would need some plugin for that as this plugin doesn't add its own mechanics it just allows you to run JS from the battle command windows.