src/renderer/component/common/icon.jsx

@@ -257,7 +257,8 @@ class IconComponent extends React.PureComponent<Props> {
 
   render() {
     const { icon, tooltip, iconColor, size } = this.props;
-    const Icon = FeatherIcons[icon];
+    // const Icon = FeatherIcons[icon];
+    const Icon = customIcons[this.props.icon] || FeatherIcons[this.props.icon];
 
     if (!Icon) {
       return null;

src/renderer/component/header/view.jsx

@@ -59,6 +59,7 @@ const Header = (props: Props) => {
           className="header__navigation-item header__navigation-item--back"
           description={__('Navigate back')}
           disabled={isBackDisabled}
+          icon={ICONS.BACK_ARROW}
           onClick={back}
         />