Looks like there is, yet, another problem with mixed-resolution setups using Maya.
My Maya subscription is going to run out soon, so I am getting a reminder whenever I start Maya. My main monitor is 4k and other monitors are 1440p and 1080p.
As you can see in the attached screenshot, I can't click the "x" on the upper-right of the pop-up window to get rid of the reminder, when the main monitor is set to 4k. I have to go into Windows Display settings and set my main monitor resolution to 1440p to get the pop-up window to scale properly.
So, basically, if I want to use Maya right now, I have to set my main display to 1440p, rather than its maximum capability of 4k.
Please, please, sort out your multi-resolution flow. This is not the only problem with multi-resolution, but just the most recent one I've run into.
Maya 2018.6
Maya 2019.3.1
GTX 1070
i7-770K
32GB RAM
Monitor 1: 3840x2160
Monitor 2: 2560x1440
Monitor 3: 1920x1080