It seems only logical to me that the plasma-applet-window-button is integrated in Latte Dock. In my opinion this functionality would be great to be offered standard by Latte.
Created attachment 117047 [details] a thought Perhaps something like this would be logical. When you click on the black flower (or whatever it may be) - attached image - the configuration window of plasma applet window button could open.
this is intentional and even further all applets currently in Latte will be published in kde store and removed totally from Latte codepage. The goal is Latte to provide only the dock/panels functionality and anything extra to be found through kde store.
If that is the direction you want to go that's great. Latte is superb!