Not sure how your popup page is currently structured, but it sounds like a ListView or Datagrid with Xpath something like this would work:
[Confirmed = false]
This assumes that the entity for the listview or datagrid is your Appointment entity.
If that doesn’t help, maybe including a screenshot or two in your question would provide more details about what you are working on.
replace the homepage by a microflow, which will check if there are unconfirmed appointments. If so, show home page + pop-up page with appointment list. If not, only open homepage.
Microflow which retrieves unconfirmed appointments and aggregate/counts the list of found appointments for performance improvements.
Pop up page displaying the unconfirmed appointments.
Thanks so much for your comments! I am however stuck once again, I am not able to add a constraint to the first ‘retrieve list’ object and the appointments found? check also gives me an error. This is the same microflow as I used before so all of the same rules should work.