Hi Simerjit Kaur,
You can create a popup page instead of using the default confirmation popup. Show the popup page with the required customization and add the Cancel & Proceed button on the popup. Proceed button action should trigger the nanoflow call.
if you want to customize your confirmation popup, you could add nanoflow or microflow with a validation to the save button which currently prompts the standard confirmation. The flow does the logic (whatever required) and opens a popup page.
If no custom validation of your data is needed, just display a custom popup page directly.
the custom popup page now can hold all your information you’d like to display the user, eg. a verification warning or an information about the next step. You can add as many buttons to the popup as you like. Clicking the buttons will then perform the action (The Confirm button will execute the flow you previously used in the standard confirmation).
Does that help?