@Ryosuke S I fully agree with you. I reported the exact same issue to dev@flexsim.com in... November 2016. And I sent a reminder to @Jordan Johnson in February 2022. I copy below what I had reported, and Jordan's answer.
Hi Jordan,
I know that the issue below has already been reported to dev@flexsim.com and is "by design" since many releases, but I still hope that one day it might be improved.
When you add cases to some pickoptions, they are added outside of the screen size and can't be reached.
For example below, I add 4 cases to a Port By Case pick option, but the cases go beyond the bottom right corner of my screen:

I know that in Orem you all have huge screens so you likely don't care about this because you never experiment it.
But not everyone has large screens like you. Especially during trainings, most participants bring their laptop (ie smaller screens than external displays), and they often get stucked in the bottom right corner of their screens.
Do you know if there are any plans to fix the drawback shown in the gif above ?
For some other pickoptions, it works much better. For example below with the Set Label by Percentage pickoption, when I add more cases the window moves up, not down beyond the bottom of my screen:

Jordan's answer (February 4, 2022):
The fact that it works in some popups makes me wonder if it's something we could easily adjust. I can see how this would be annoying for users with smaller screens during training. I'll up the priority on this issue.
@Jordan Johnson what's the current priority of this issue ?