When you open the multiselect, it doesn't honor the viewport. When there's too little room at the bottom, it should open on top of the initial dropdown, the same way a default select would behave.

This:

Should behave like:

first mentioned here: jacobworrel/react-windowed-select#31

I've found that if I use a height format other than a pure number, such as "100px", it breaks so hard I have to force kill my Chrome tab. Easy enough to fix, but it might be worth noting in the documentation that heights must be provided in only that format.