Go into Chart of Accounts – highlight the accounts you want to set the code to be mandatory on. You can do this multiple times, so you don’t have to try to highlight them all at one time.
I selected to filter on all Income Accounts – selected the Income/Balance column. Set the Filter to this Value
Select all the Rows
Select the Dimensions from Navigate, Account, Dimensions, Dimensions-Multiple
Then Dimensions Multiple – should be your only option is you have multiple lines selected
Select New
Enter in your new Dimension code and set the Value Posting field to Code Mandatory – then select OK