how to convert existing project from resource control to task control?

in Go live we opened a project with budgetary control "resource control" level mode. (we are working with the system since 1.1.24)

Now we want to change the budget control mode to - budgetary control "Task" level mode.

I can see that the budgetary control can not be override (it's gray). is there any way to change it without closing the project and create a new one ?

Because the project is still alive, the value is unique and part of the COA.

If it can not be override is there a "best practice" to convert old project to the a new one, with all it's content? (sub ledgers transaction etc..)