Hi @Juter,
I suggest that you kudo and comment on the Wish List item that you found as that is the best way to provide suggestions for new features in JMP.
My personal opinion is that setting a preference so that all variables on all graphs are reported with a fixed number of decimal places is not something that many people would want to do. JMP is designed as a comprehensive exploratory tool for all different kinds of science and engineering data.
A better solution (again my opinion) is to select all your relevant columns in the table, then use Standardize Attributes... (from the Cols menu) to add an Axis Column Property, where you can define the exact format in which these variables will be presented on the axes. I did this for the height and weight columns in the attached example.
I don't know if that would set the decimal places for every report - it probably depends which reports you are using.
If you need to do this a lot then you can maybe write a script that would add this Column Property for all continuous columns in a data table. Workflow Builder should give you a good start on that. Or, if you need it to be more flexible, you could even write an addin.
I hope this helps,
Phil