Feels like such an obvious feature I was surprised to find out it wasn't possible, you should be able to choose which monitor notifications show up on and ideally which corner of that chosen monitor as well
I am not sure that I understand what ShaunDreclin wants. So I do not know if my comment is related. When Thunderbird downloaded mail, I used to get a pop-up window in the lower right that told me the number of messages and the subject lines. I recently upgraded from 115.13.0 to 128.0.1esr, and not these notifications are part of Windows Notifications. Windows saves only the last 20 of these notifications, so when I get lots of mail (I will be glad when the election season is over) I can easily have over 20 of these (somewhat useless) notifications waiting. And, since Windows saves only the last 20, there could be a notification from another program that is lost. I went into Settings --> Notifications to disable notifications from Thunderbird. Now I get no notifications when new mail has arrived. I did not mind the old notification pop-up that went away after five seconds; it told me the subject lines of mail messages when I was at the computer; when I was not at the computer, there was nothing cluttering anything (except my inbox).