I just spoke with a professor at Ohio State who was struggling with the interpretation of effect coding as he teaches this topic to his students. He suggested that adding the non-included group to the table of parameter estimates (but likely excluding any statistical testing details) would help his students better understand the meaning of these parameter estimates.
It is a pretty common need to have students calculate that final group parameter "estimate," either by hand or by using the Save Columns > Prediction Formula and then copying the value out of the prediction formula. In STIPS and on SKP (https://www.jmp.com/en_us/statistics-knowledge-portal/what-is-multiple-regression/mlr-with-categorical-predictors.html) we advise students to use the prediction formula to find this value, but it would be much simpler if it just appeared in the table of estimates. Could the "estimate" for the final group appear in the output, but with no statistical details and possibly in italics or with some other indication that this "estimate" is determined fully by the other estimates in the list?
Here is Big Class, with a model using nominal Age to predict weight. Age 17 is not included in the parameter estimates table because of the singularity.
Instead of reading it from this table, we ask users to go to Save Columns > Prediction Formula to view in the formula the value that is calculated for the 17 year olds:
I see a similar idea in part B of this unanswered Community post: https://community.jmp.com/t5/Discussions/weighted-grand-mean-with-effects-coded-MLR-showing-the-last/m-p/251792
