radio/checkbox in drop-down menu radio only

Hi

I am using the “Rradio/checkbox in drop-down menu” option for my filters, but I can only see radio buttons on the dropdown menus. According to your documentation checkbox is an option, but I cannot see how.

https://products-filter.com/extencion/radio-or-checkbox-drop-down/

I looked at the filter options but on the dropdown menu labelled “Type” there is only the “Radio” option listed. How can I switch to checkboxes?

Your help will be greatly appreciated.

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