There are certain functions that are performed on the server (meaning after the information you enter on a page has been transmitted to WikiTree) and writing to the database is among these. There are other functions that can be performed on the client (meaning by your browser before you transmit the page to WikiTree) using javascript. Once you transmit the information to WikiTree, it is no longer available to your browser.
The only way to do what you are asking for would be for WikiTree to create a new page, populate it with the information you submitted, and send it back to you. This would require a significant amount of programming effort to do (including only doing it when a processing error is encountered) and would use a significant amount of server resources (which would slow down other things being done by the server at the same time).
I understand your request, and you have a very good reason for asking for this, but unfortunately the extra work and overhead required to do it make it unreasonable to hope that it will happen.