When the system comes out of screen saver or sleep mode, the Control palette has disappeared. The only way to make it visible again is to quit and restart the program. InDesign Version 16.1, macOS 10.14.6 Mojave, 2013 MacBook Pro (Retina, 15-inch, Late 2013). Two monitors: built-in retina display 15.4-inch (2880 x 1800) with NVIDIA GeForce GT 750M 2 GB graphics and 19.5-inch (1920 x 1080) DELL D2015H Display also using NVIDIA GeForce GT 750M 2 GB graphics. Problem seems to be related to the use of two monitors.