I'm having problems styling a fairly simple tree panel.

Code:
Ext.define('stuff.view.layout.Menu', {

    extend: 'Ext.tree.Panel',
    alias: 'widget.layout.Menu',
    animate: false,
    store: 'stuff.store.Menu',
    bodyPadding: 5,
    lines: false,
    rootVisible: false,
    border: false,
    bodyBorder: false,
    initComponent: function () {
        var me = this;
        Ext.applyIf(me, {});
        me.callParent(arguments);
    }
});
This code is in the folder /app/view/layout/Menu.js

All works fine, but in my custom theme (basically just Neptune at the moment), I cant seem to use the css styles in the file
sass/var/view/layout/Menu.scss to override tree panel variables. They are just ignored when I build the theme.

However if I create a mixin in /sass/src/panel/Panel.scss I can set the 'panel' mixin overrides and these are picked up by the tree panel. Unfortunately, the settings I want to change are tree panel related not panel related.

I suspect I'm putting the file in the wrong place - but wondered if this is a known issue. The tree panel works fine by the way, and all builds without errors - its just not picking up the styling changes.

Any help appreciated.

I'm on 4.2.1

Thanks