How do post-it notes automatically shrink?

Move the cursor to the bottom border of the note. When the cursor changes to the up-down arrow state, press and select it with the left mouse button, and drag the mouse up to shrink the note window.

In the basic system settings of the note, you can also turn on the top simplified mode. When the top simplified mode is turned on, more notes will be displayed in the content list than in the default simplified mode on the notebook window of the same size.