So, to come back to your original question: is there an action to resize covers? The answer is no. And this should have been the result of the linked thread.
In that linked thread there were mentioned a couple of tools.
If one does not exist any more, look for another one.
MP3tag has web source scripts that look mainly for tag information and also can download the pictures found with that tag information.
If you look for other programs to download pictures (which is a completely different thing than an action to resize), you may have a look at this thread:
or look for albumartdownloader.