Since JMP 18 there is conditional formatting and semantic formatting to allow for specific rules of key figures in reports:
You may take a look in the JMP help on that to see if that is covering all what you need.
A default set for all data (incl. data table values) is in my eyes not really useful, as it is likely that some data one imports has a specific format which cannot useful displayed with 2 decimals. However, the above should come close.
If you need to change the format for all your continuous data, select all columns, right click on one column header name and select standardize attributes. There you can specify the format for all data in one single step.
This step can also be scripted and saved in your menu as an entry. That way every time you open data table you can apply the script by pressing the menu item (running the script behind the scenes).
There might be someone who has done something like that already or can chime in with a small script