As Yupput is open source, you may adjust Yupput's default CSS in any way you want. However, here are some adjustments that may be of interest to you.
Attribute(s) with default(s)
↳ position: absolute;
↳ top: 22%;
You may change the position of Yupput's outer container to fixed if
you want to have a sticky dialogue that will not scroll with your viewport.
Ytils' Yupput demo uses this override as well.
top: You may change the top appearance of the Yupput dialogue to a more suitable setting in case you changed the .maxItemCount configuration option.