Modals is a fantastic product and has many uses. One of our uses includes distributing important messages after a user logins to the website. This was meant to address the 'I never saw the message' issue we had when sending emails or posting in other areas of the site. However, even though users login and can't do anything else until they close the modal I still get 'I did not know' statements from employees. What I would like to be able to do is have a message presented to users with an 'Acknowledge' button, and when the button is clicked they will no longer see the message (core function) and a record is recorded showing that user acknowledged the message. I can see that due to the many ways that modals is used that this is not as simple as it may seem. We use modals with articles which have IDs and if we simple had a table that contained the article ID, User ID, Date/time, we would be good to go.
There is no option for what you want in Modals itself.
Modals does not store any type of user data to the database.
So you would have to code that part yourself. Create a button that triggers code that stores what you need.
Then based on that data, conditionally output the {modal} tags.
Or find an extension that does that out-of-the-box.