This bug report related to other report #575621.
Short description for this wishes is "Give users display DeltaT value in GUI", for full description I copy part of comment by Allan Johnson:
One more thing that would be really helpful for evaluating is if we could have Stellarium display the value of Delta T currently being used for whatever date it's displaying. It would be nice to be able to browse past the years -500, 500, 1600, 1700, 1800, 1860, 1900, 1920, 1941, 1961, 1986, 2005, 2050, and 2150, watching for any unexpected discontinuities at these points. Also if we had a display of the Delta T value, it would be easy to check as many dates as desired against the Delta T values listed in NASA's catalogs of Lunar and Solar eclipses.