Hi,

1) You need to make sure, you have correctly created a filter:

- Create filters
- Assign filters to products
- Assign filters to categories

2) Then you need to export module to Page Builder:

docs.themeburn.com/burnengine/content-blocks/opencart/

3) And finally, you need to go to Page Builder > Right / Left column > Level 2 categories and insert the newly create filter.

BR,
ThemeBurn team