I was not able to resize the window of the WhatsApp Desktop application and even if i have uninstalled the app and install it back, the fullscreen persisted.
You can solve this by doing the following:
– Close Whatsapp and open the following file with notepad:
– Change “isFullScreen”:true to “isFullScreen”:false
– When you now start Whatsapp it seems still maximized, but you can resize it again.
Hint: The workaround did not work for the WhatsApp Desktop version download via Microsoft store.