ARS 19.08 introduces a new option to improve performance using subquery algorithm. See "Performance improvement by using Subquery algorithm" in https://docs.bmc.com/docs/ars1908/19-08-enhancements-866348750.html
This feature can only be enabled by making modification on form level.
As it is not recommended to create overlays on CMDB classes the change can only be implemented with Developer Studio in Base Development Mode. However this action raises the problem, that in case of upgrades/patches reimporting these forms, the modifications are lost.
Similar scenario when you want to eg. change the result list on the class forms like eg. BMC.CORE:BMC_Computersystem to display usable information. You can do the change only in Developer Studio using Base Mode.
It would be great, if class manager would provide additional means to make such form changes.