After clicking Add new Custom side panel will be displayed with custom creation form. User has input field to fill in deatils, option to attach the files related to the custom.

Column labels are displayed based on the configuration done at the admin side of the collection.
User can fill the input fields of different parameters and click on Create button. Creation form of custom can be see in the below image. clicking on Cancel button will close the sidepanel and will cancel process of creation.

After clicking on Create button, user will displayed with details page of created document in the side panel and will have View Details and Close button.