The quick buttons for logging diaper changes can be found in the upper part of the app.
The buttons are designed to be able to quickly register a diaper change at the current moment. The two icons indicate how "wet" and "solid" contents. Click one or both as needed. A save-button will appear afterwards:
You can also add a note to the diaper change by clicking the notes button:
Press the save button to record a diaper change. That is it, easy as that.