Datacube target usage to open/close grouped sets of rows


I am experimenting with the Datacube for some visualizations where i need a tree based hierarchical view of my dataset and it fits really nicely

The only problem I had is the usage of the Target field, I really cannot wrap my mind around the usage and it seems there is no documentation

My objective is far similar to this post, to be able to programmatically control the opening of the tree

At now I didn’t find any documentation neither sample on how to set the target parameter to open a grouped set from a callback or at the start