There is no built-in way to send action bar messages to players without running the "/title" command from the console. We need access to this class "net.md_5.bungee.api" which has the "ChatMessageType" and "chat.BaseComponent" subclasses responsible for sending the actionbar text.

I don’t have a deep understanding of how Scriptcraft works yet, but if your server is run on CanaryMod, Bukkit, Spigot, or Paper, you may want to check their API for something similar that you could use.

Bukkit API : https://hub.spigotmc.org/javadocs/bukkit/overview-summary.html
Spigot API : https://hub.spigotmc.org/javadocs/spigot/overview-summary.html
Paper API : https://papermc.io/javadocs/paper/1.13/overview-summary.html (I think that this one may be outdated)
CanaryMod API : https://ci.visualillusionsent.net/job/Canarylib/javadoc/

I hope this helps and if you do happen to find the answer, please let me know as well by replying here. Thanks.

https://github.com/Magikcraft/magikcraft-core/blob/master/actionbar/index.ts

JavaScript version: https://github.com/Magikcraft/magikcraft-core/blob/master/actionbar/index.js

Alright, with help from jwulf, I was able to create a working action bar script, however it does require you at least have spigot installed, not just bukkit.

var jx = {
   color: function (text) {
      return text.toString().split('&').join('\xA7').split('\xA7\xA7').join('&');
   },
   player: function (name) {
      return server.getPlayer(name.toString());
   },
   actionBar: function (target, message) {
      try {
         var bkClass = Java.type('net.md_5.bungee.api.ChatMessageType').ACTION_BAR;
         var bkClass2 = Java.type('net.md_5.bungee.api.chat.TextComponent');
         jx.player(target).sendMessage(bkClass, new bkClass2(jx.color(message.toString())));
         return true;
      } catch (error) {
         return false;
      }
   }
};

jx.actionBar('Notch', '&aHello there!');
// returns false on bukkit servers
// returns true on spigot/paper servers