Developing plugin, create a call to a page not listed on the wp-admin menu

Please help me to understand a concept.

When developing a plugin, I have pages linked from the wp-admin menu using add_menu_page and add_submenu_page.

On one of these pages, for example, I list all the database entries that have been created for this plugin, say, a list of events and performances.

For each entry shown, I want to have a summary of all the commands that can be performed on it, like delete, set inactive, edit etc.

To delete the product I want it to go to a screen that shows the entries details and has a delete button.

This is my question: What is the proper way in WordPress plugins to have a new php page that you can call when the page is not linked to from the wp-admin menus with add_menu_page?

I hope the above makes sense. As I’m obviously struggling with the concept I may have missed the obvious.

Thanks