Hi zenbob1,
The styling for the mobile dropdown menu is handled by the Wedge Theme styles and is not directly related to the Post and Page Builder. There is a + icon inside that box on mobile devices, but it looks like it is using the same assignment as the background, so the box appears empty. Changing the color of that icon will make it visible and should help inform users that clicking the button will provide them with more options. The easiest way to make modifications to that button is add some custom CSS using the tool located under Advanced > Custom CSS in the theme Customizer.
Here is some CSS that targets the icon inside the button and changes it to the same purple color used elsewhere on your site.
.navbar-nav.sm-collapsible .caret:before, .navbar-nav.sm-collapsible .caret:before { color: #a347ff; }
The Wedge theme is not publicly available through the WordPress theme repository and does not have it own support section on ww.wp.xz.cn, but if you ever have any other questions related to that theme you can reach out to us through the support forum on our website.
Please let us know if there is anything else that we can do to help!
That did the trick, thank you so much Joseph! I really appreciate the help.