provide the combination of "child table" with "hierarchical" mode

[zonky2]

At this time, it´s not possible to use ~~variants or~~ hirachical data at a child table, because both use the column pid...

May be we can change the builder https://github.com/MetaModels/core/blob/master/src/MetaModels/DcGeneral/Dca/Builder/Builder.php#L656 to use self definited column(s) as parent id

may be this old row https://github.com/MetaModels/core/blob/84b229f46ddbfcc112278a228c893cf63ae6d791/src/MetaModels/DcGeneral/Dca/Builder/Builder.php#L656

now at https://github.com/MetaModels/core/blob/065ed3d9e2dc4f98b947290962bf279958973a25/src/CoreBundle/EventListener/DcGeneral/DefinitionBuilder/AbstractConditionBuilder.php#L178

[zonky2]

At MM 2.3 it´s possible to use variants as data at a child table