Is it possible to add another translation selector to the bottom of the form?

Unfortunately, it's not possible. A workaround would be to have it fixed on the form so even if you will scroll to the bottom, the selector will stay in its current position. You can inject the following custom CSS codes to do that:

div#langDd {

    position: fixed;

    top: 20%;

    margin-right: 15%;

    z-index: 1;

}

You can add a background color to the selector to make it noticeable, add the following custom CSS codes:

div#langDd {

    background: #555555;

    color: #fff;

}

Here's our guide on how to inject the custom CSS: https://www.jotform.com/help/117-How-to-Inject-Custom-CSS-Codes. 

The result would be like this: