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:
“C:\Users\<username>\AppData\Roaming\WhatsApp\settings.json”

– 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.