The XUI Views library is a B4XLibrary which is a zip file.
Eme Fabionacci explained you what to do.
When you unzip the XUI Views.b4xlib file you find one bas file for each view.
You can modify them, zip all the files and sub folders again and rename the .zip extension back to .b4xlib.
The main drawback in doing so, is that you have a personal library and when Erel updates it, yours will not be updated.
Another suggestion is to post a wish thread for this.