The Preferences for asset libraries are becoming more than a simple name + path. E.g. there is now an Import Method options, and we previously also considered a Relative Paths option (which we may still want to add). The previous UI, while consistent with the Auto Run Python Scripts UI isn't well suited for less than trivial cases. Using UI lists makes the UI more scalable and follows usual list UI patterns more. There is also more space for the path button now. Part of #104686.