My issue is with how the advanced filter (defaulted in footer) interacts with the horizontal scroll bar.

If I don't set my tables to horizontally scrollable, then on a mobile devise, you can't see more than 5 or so columns.  Making it horizontally scrollable is useful.  However, when one tries to use the advanced filter, it drops down behind the scroll bar.  A vertical scroll bar is automatically generated so one can scroll and use the filter however, most of my users miss this and never realize the filter drop down is behind the scroll bar. 

How can I change this?

It's the same for all tables.  Scroll to the bottom of this page and use the filter below the "Disease" column in the Infectious Disease Table.

https://www.lcdhd.org/info-tools/health-assessments-and-statistics/health_report_card/infectious-diseases-including-hiv/

We were able to work around the issue by choosing the "scrollable" option, and then inserting the following Raw CSS code into the page:

<style>
.selecter-options {
    position: relative !important;
}
</style>

I would recommend that, in the Table Editor, under Additional Settings, you add the option to set the "selector" to either "absolute" (the present default) or "relative".  It could be an option below "Advanced Filtering" when both "Advanced Filtering" and "Scrollable" is selected.  It could be described as, "Allow filter drop down to push down horizontal scroll bar."

Look at this page: https://www.lcdhd.org/info-tools/health-assessments-and-statistics/health_report_card/socioeconomic-indicators/.  Scroll down to the "Other SocioEconomic" Table and use the filter below the "% of Appropriate Population" column to see how this enhances the table filter when used in conjunction with the horizontal table scroll.

This seems to work good on both a desktop and a mobile devise.