It is important to distinguish between a zero value and a missing value. However, if you label a bar chart in Graph Builder with values and the value is zero, then the label does not display. The reader of the chart no longer knows if it was a recorded zero or a missing value.
There seems to be no way to force the 0 label onto the chart. Trying to make the value non-zero (i.e. 0.00001) just makes the label show the value - you cannot change the numeric detail of the label (which is a problem already noted: https://community.jmp.com/t5/Discussions/How-to-change-number-of-decimal-places-in-Bar-chart-labels-...)
A solution already shown for zero values (
https://community.jmp.com/t5/Discussions/Show-zero-percent-in-bar-chart/m-p/208592) seems to only work for percentages, which my dataset does not have.