Since Pimcore 5.x, grid configuration operators are available to display calculated values in special columns of the object grid. The operator "PHPCode" can be used to create individual getters.
The class can be located anywhere that the autoloader can find it. The easiest way is to store the class in the AppBundle. The folder structure in the AppBundle then corresponds to the namespace that must also be specified in the Pimcore backend. If the class "MyCustomCalculator" is stored in "src/AppBundle/Export/Calculator/MyCustomCalculator.php", for example, the following must be entered as the calculator in the Pimcore backend: "\AppBundle\Export\Calculator\MyCustomCalculator".