To see how to use HUDs and GUIs API (Font Images) you can check my examples.
Access mana bar value example
PlayerHudsHolderWrapper huds = new PlayerHudsHolderWrapper(player);
PlayerQuantityHudWrapper manaHud =
new PlayerQuantityHudWrapper(huds, "magiccraft:mana_bar");
if(manaHud.exists())
manaHud.setFloatValue(2.0f);
else
System.out.println("Error: mana not found, maybe it's disabled.");
Get Emoji or GUI character
new FontImageWrapper("twitteremojis:confirm").getString()