PX UI feedback: make gray buttons more visible

When building an engagement, there are several light gray buttons that are barely visible in the app. I was building a Slider and nearly missed the option to copy a slide (very helpful!), and I didn't see how to re-order the slides (also great!) simply because the icons for these actions are too subtle and grayed out unless the user mouses over them.

@lauraramosrp Another useful tip!!

Agreed, it also took me a while to find these functions which is a little silly since they are so useful and important.