On the SMARTDAC+ series GX20, tag numbers appeared in the numeric display on trend graphs when 10 channels were assigned to a display group. However, if I assign 20 channels, the tag numbers don't display.

If you increase the number of assigned channels to one group (not only on the GX20), lack of space can result in some characters being truncated. To view the tag numbers, double-tap the numeric display in the trend screen to display "Channel Info."