It is not possible to delete the application which is assigned to configurations.
To unlink an application from the configuration, find the application in the applications tab, click the "Configurations" icon, then set "Do not install" for all configurations.
![](https://h-mdm.com/wp-content/uploads/do_not_install.jpg)
Please note that the "Delete" action DOES NOT unlink the app from the configuration. The "Delete" action forces the app uninstalling on the devices, whereas "Do not install" means "do nothing".