You can change the URL title with the following steps:
In some cases it may be needed to customize this HTML, which can be done by creating a file called index.html in the theme/web folder. To make sure that your file has the right structure, we recommend you copy index-example.html from the deployment/web folder to the theme/web, rename it to index.html, and then use it as a starting point. This file will be created after you have deployed your app locally at least once.
In this files you will see the title ‘Mendix’. You can change this.
Read chapter 9 from this page:
See also where Chris de Gelder gives the answer as well:
Have you tried to change the application title? In Navigation > General, you can set a different name other than “Mendix”:
I hope that helps you, best regards!