Adding a Lovelace card that acts like a true popup window would be very helpful. Having 4 states (general - no icon, Info - w Info icon, Warning - w Warning icon and Critical - w Critical icon) and two or three configurable buttons ( OK, CANCEL) as a basic minimum.
This would differ from Persistent notification in that the window would pop up on top of the current active window. Some users have asked for a configurable More Info window. This proposal could cover that scenario as well as uses where the user needs to act immediately.
May I respectfully disagree with WTH?! No custom pop-up out of the box? being marked a duplicate of this?
I think that other WTH is about creating modal dialogs, filled with cards. While this one is very specifically talking about confirmation dialogs with one icon and a set of buttons.
I think both are reasonable suggestions (even though I’m personally only interested in the other), but they aren’t the same to me.
@hheimbuerger
I believe he may be referring to this WTH post, with yours being a duplicate of that post, not mine. Just my thought.
https://community.home-assistant.io/t/wth-cant-i-use-a-card-as-more-info-popup/802493/14
Neither of them is my post, but that’s besides the point. 
I think you’re right, and I can see how No custom pop-up out of the box has some duplication with what’s being discussed on WTH can’t I use a card as more-info popup (even though the title is quite off).
But the fact is that this here topic is what it’s flagged as a duplicate of. And I think they are quite different.
I also think your topic is a separate request.
Can you tell us more what the use cases of such a card would be?
Sure, and thank you for asking. My primary goal was t have a card that would pop up on top of whatever task the user is currently doing, so that they can respond quickly to the event that triggered the popup. Typically that event would be something that is important to respond to right away. In my home I monitor my circuit breaker panel via the devices connected to each circuit. One circuit s particularly sensitive and trips often. Having a (silent) popup alert avoids other, more intrusive actions such as blinking lights, a sound or voice alert or other actions.
Of course there are other uses such as perimeter access doors, alarm systems, air quality or smoke/fire/water sensors that could benefit. Beyond the critical alerting realm, the card could also be used as a “are you sure” type of last check, especially with configurable option buttons, such as OK, CANCEL, YES, NO, CONTINUE, etc. I do know that Buttons can be configured with a confirmation, but I don’t think it can be configured to act as I described above in the case of a tripped breaker.
Although I make no claims to understand the underlying operation of Home Assistant, I believe this card would operate in much the same manner as a More Info popup works. I also believe that if this idea is implemented as a standard feature of HA, users will find even more ways to use the feature.
I hope this helps you understand my desire to have a configurable true pop up window that can be called from automations, scripts, events or other methods that I have not considered.
Please feel free to ask if you have any other questions. Thank you.
Art
aka kartcon