Under "Hovering", "List" doesn't work

What if you choose "Show thumbnail preview (default)", does that work? I suspect that it's not the tweaker's fault, since the implementation of that option is quite simple. It can also be enabled via registry without the tweaker, see:

https://www.tenforums.com/tutorials/20989-change-taskbar-thumbnail-threshold-show-list-windows-10-a.html

You can exit the tweaker, try this method, and find out whether the problem is related to the tweaker or not.