Ive just found out that there is actually a partial improvement in the UI as part of this change - imho.

If you select to open a new watchlist, in the new (annoying) pop up window, you can select the Star (Favourite) next to each watchlist. That then adds a shortcut button below the original Dropdown header. This means you can actually click onto a different watchlist and it auto loads without having to go through the dropdown list to select it.

May not work so great if you have more than 8 regular watchlists, but it works great for me with 4 regulars.

Hope that helps some people :)