Go to "Global Connections" under the "System" folder. From there, take a look at the "Display" tab, in particular the "Remote Display Number", "Close an On Top Display" and the "Close All On Top Displays" connections. Read the help file for this tab. This will give you the backbone for what we're going to do. You will need to add either PLC or HMI tags to these connections. Each display you work with will need an unique display number.
Under the "Logic and Control" folder in the Explorer right-click on the "Macros" heading and then "New". This will open the Macro editor. Under the "Tag" heading put the tag name in that you assigned to the "Close All On Top Displays" connection. Put "1" under the expression. This will close all of your open "On Top" displays. In the second row put your tag for "Remote Display Number". Assign this the value of the display number of the screen you are trying to open. Press OK and save the macro with a relevant name.
We now need to make sure that we reset the "Close All On Top Displays" and "Remote Display Number" tags so that the HMI will continue to function and allow screen changes. Make a new macro and set the tags you are using for those two connections to "0". Press OK and save the macro as your "Shutdown" macro.
Go to your test pop up screen. Under display settings, set the "Shutdown" macro to your second, shutdown macro. This should reset the tags that you are using above to zero and allow the HMI to continue functioning and allow subsequent screen changes.
Now that you have tags and macros for this try creating a "Macro" button: "Objects" --> "Advanced" --> Macro. This will be the button that loads your popups (not a "Goto Display" button anymore). Configure this button to run your macro.
When pressed, the button should launch your first screen change macro. This should close all of the "On Top" screens and then load your new screen after that. Hopefully
Test.
I haven't tried this exact method myself (I would typically use the PLC to reset variables) and it may not function depending on timing of screens opening. If this method doesn't function properly it could reset in your HMI being unable to change screens. I'd recommend that you create numeric entries for the HMI tags listed above on your test screens so that you can view and reset them easily.