Wow. I was about to ask this
question. Just before typing, I read the above message, found the answer. Brilliant!!
Would you know how to "appletize" the extension "Iconized Windows List" which is currently out of order?
I tested about most of the extensions in the PPA to Cinnamon 1.3. Like said further above, they work, if you add this "1.3.1" snippet in their relevant metadata.json file. The only one unstable seemed to be "Removable Drive Menu
But, on the other hand, I think most of them will have to be transformed in applets because they sit in the panel. Just like the weather
extension above. This will keep your Cinnamon panel flexible and enable you to claim insurance damage if need be.