Hi Bill, 

I see what your trying to do here. I would recommend making the action on the click to open the sliding panel a multiple actions (action). Close the top most panel then toggle the sliding panel. 
On close of the sliding panel you can then force your popup to open to go back to the original state of the page. 

Let me know what you think of this idea. 

I am not sure it will know which popup to re-open?

Matt’s approach would work. With his approach, the user would need to reopen the pop up after interacting with the Sliding Panel.

Another approach would be to change the z-index of the sliding panel with custom CSS so that it would appear in front of everything.

How and where would you suggest i put the css?

You’d have to find the exact one for your page but this is the one I found in a basic repro page I have made. The highest z-index score will show on top. You can set it to 58 if your heart should desire. But if something else is 59, then it’s been beat!

Is there any plane to have popups and sliding panels resect each other like popups respect popups?

How so?