Hey Jim,
There is no submit button for the inbuilt search or an option to include it.
Please link to the scanner you use as unfortunately all of these tools give different reports and I have never had this come up before.
In either case if you want a customised search or to add to it then the recommended way to do this is copy the current HTML output of my search, turn search off, copy the HTML to the additional content section and you can then add in the button easily from there.
Hope that helps
Peter