List of selected in Outliner collections

There is no single selection list for collections. We can open the Outliner in two different Blender areas, and select a different set of collections in each of them. Since the list of selected collections is different for each Outliner area, it can only be obtained through the context of this area.

Read more: https://b3d.interplanety.org/en/list-of-selected-in-outliner-collections/