If you have your data table reference in variable dt, scrip below should work
Column(dt, "Error(%)") << Set Name("Error_Percentage");
![jthi_0-1676009430466.png jthi_0-1676009430466.png](https://community.jmp.com/t5/image/serverpage/image-id/49988i817A00CB6EFB3852/image-size/medium?v=v2&px=400)
Also if you have JMP16+ you can get script like this from action recorder:
// Change column name: Error(%) → Error_Percentage
Data Table("Untitled"):"Error(%)"n << Set Name("Error_Percentage");
-Jarmo