data-ajax-params="['action','get_county_list']['param2','value2']"
SOW Ajax plugins are using this format – dedicated for ajax requests and its purpose is to send additional params to your backend!
You can add as many params as you need, keeping the same format.
Their equivalent is this:
<input type="hidden" name="action" value="get_county_list">
<input type="hidden" name="param2" value="value2">
Params are often needed in POST methods because on GET we can use the usual:
?action=get_county_list¶m2=value2&....
So if the plugin is using data-ajax-params, you can use the way you want/like for GET methods.