MrSteveVee
Thank you.
The monitor's setting is 1024x768, the maximum. This was the setting before. Opened Darktable 3.2.1 on this monitor setting, the window of Darktable extended outside of the monitor screen. Then, the setting was altered to 1366x768, the display size of the monitor became smaller than the screen, about 2/3 of the screen size, a square at the center of the monitor screen. Tried many different settings and found the 1280x768 setting (1) filling up the entire screen, and (2) all panels of the Darktable displaying on the monitor screen after some adjustings (squeezing the panels inside of the screen boundary)
Thanks.
Fotojoy.