ただのEならわざわざ画像なんて使わなくてもそのまま書いちゃえばいいんじゃないの
フォントの方が見た目変えるの楽だし

(function(){
var alias1 = ItemListScrollbar.setUnitItemFormation;
ItemListScrollbar.setUnitItemFormation = function(unit) {
alias1.call(this, unit);
this.weapon = ItemControl.getEquippedWeapon(unit);
};

var alias2 = ItemListScrollbar.setUnitMaxItemFormation;
ItemListScrollbar.setUnitMaxItemFormation = function(unit) {
alias2.call(this, unit);
this.weapon = ItemControl.getEquippedWeapon(unit);
};

var alias3 = ItemListScrollbar.drawScrollContent;
ItemListScrollbar.drawScrollContent = function(x, y, object, isSelect, index) {
alias3.call(this, x, y, object, isSelect, index);
if (object === this.weapon && object !== null) {
TextRenderer.drawSingleCharacter(x + -8, y + 10, 'E', ColorValue.DEFAULT, TextRenderer.getDefaultFont());
}
};
})();