Filter sidebar widget missing in configuration

[cairabbit]

I'm using Smartstore version | 4.1.1.0 and paid.
As per the documentation says:
Allow filtering in the Specification Attributes only takes effect with an active filter sidebar widget.
And filter sidebar widget is at "Configuration -> Settings -> Catalog -> Product List", however, no "Filter sidebar widget" can be found.
Then I googled, found this link : http://community.smartstore.com/index.php?/topic/49485-filter-sidebar-widget-missing/
The product attribute filters and Enable specification attribute filters are activated in my Plugins > MegaSearch. But I still couldn't find the "Filter sidebar widget" in either "Configuration > Settings > Search" or "Configuration -> Settings -> Catalog -> Product List".
Can anyone tell me where to active the "filter sidebar widget" or how can I use the Specification Attributes filter?

Below are some screenshots for the mega search settings and specification attributes

But no "Filter sidebar widget" in "Configuration > Settings > Search" or "Configuration -> Settings -> Catalog -> Product List".

I appreciate any helps. Thanks in advance.