About the Trackpad Handwriting input source on Mac
If you have a trackpad, you can use the Trackpad Handwriting input source to enter Chinese characters and punctuation with your finger.
Before you can use Trackpad Handwriting, you must add it as an input source (when you do, a Chinese input source is also added). Then choose Trackpad Handwriting from the Input menu in the menu bar.
If your Mac has a Touch Bar, you can customise the Control Strip by adding the Handwriting button 
. See Customise the Touch Bar.
When the Handwriting window is open, you can’t see or move the pointer on the screen. To use the pointer without closing the window, press the Escape key; to resume handwriting, click anywhere in the Handwriting window. To close the Handwriting window, press Control–Shift–Space bar or click Close 
in the top-left corner of the window.
To learn how to use Trackpad Handwriting, switch to a Chinese input source in the Input menu, choose Help from the Input menu, then search for “handwriting”.