System variable 1076 enables you to save the overbooking setting as a user setting.
This means that the system will remember whether you have turned overbooking on or off.
Normally after enabling “Allow overbooking” it will be set to false again after closing the task card. This is so managers not overbook by accident or forget that they have enabled overbooking.
With System variable 1076 set to true, the system will remember that overbooking is allowed.
Simply navigate to Settings, System variables and search for “1076” and enable it.