To use the pointer without closing the window, press the Esc (Escape) key to resume handwriting, click anywhere in the Trackpad Handwriting window. When the Trackpad Handwriting window is open, you can’t see or move the pointer on the screen. If your Mac has a Touch Bar, you can quickly open the Trackpad Handwriting window by adding the Handwriting button to the Control Strip. To use Trackpad Handwriting, you must add a Handwriting input source, then choose Handwriting from the Input menu in the menu bar. If you have a trackpad, you can use the Trackpad Handwriting input source to enter Chinese (Traditional or Simplified) or Cantonese characters and punctuation with your finger.
Install and reinstall apps from the App Store.