Have you already tried different plugin orders?
Viewing post in [RPG Maker] WYSIWYG UI Editor - Main Menu comments
Yes man, It gives the same error and we don't rlly know why
cannot read property 'x' of undefined
```TypeError: Cannot set property 'filters' of undefined
at Scene_SkillTree.Scene_MenuBase.createBackgroundFilters (MK_UICustomizer.js:2507)
at Scene_SkillTree.Scene_MenuBase.createBackground (MK_UICustomizer.js:2457)
at Scene_SkillTree.Scene_MenuBase.createBackground (MK_UICustomizer.js:2534)
at Scene_SkillTree.Scene_MenuBase.create (rmmz_scenes.js:1193)
at Scene_SkillTree.create (Rosedale_SkillTree.js:1746)
at Function.SceneManager.changeScene (rmmz_managers.js:2134)
at Function.SceneManager.updateMain (rmmz_managers.js:2106)
at Function.SceneManager.update (rmmz_managers.js:1986)
at Function.Graphics._onTick (rmmz_core.js:811)
at TickerListener.emit (pixi.js:9093)```
Well, usually I would have asked you to ask the Rosedale dev for support, since I don't own this plugin. Unfortunately, he passed away while ago.
I quickly made this fix: https://downloads.aerosys.blog/plugins/MK_BackgroundSpriteFiltersFix.js (right-click, save as...)
Please tell me whether it's working for you, then I can integrate it to plugin for everyone.