Hello,
I found a post about this from May, 2016 for Joomla 2.5 but I need further information
I am running 3.6.5. Those posts recommended that I add the following to the module style.css:

BODY #rt-main-surround {z-index:1;position:relative;}

I tried this using "add custom css" but it did not work, and has no effect in the module's css, or the templates css.

Where can I change this 'z-index' value so that the slider doesn't cover the dropdown menu?

Joomla 3.6.5 - Protostar template

Hello,

Send a link to a page where the problem occurs.

Regards,
ARI Soft

Hi,
I did find the answer to this issue. It works very well.

/* The following css class replaces code in styles.css at: root_folder/modules/mod_ariimageslider/mod_ariimageslider/js/themes/default
It allows dropdown menus to be in front of the slider.*/

.ari-image-slider-wrapper

{

margin: 0 auto;
z-index:1;
position:relative;

}