I just tested it and it worked for me. I created 2 groups, group1 and group2, containing the respective descendants of Cluster1 and Cluster2. I checked in the preview, that VM objects are included. Then I added a container overview and an object list. Set filter in the object list to show objects of VM type only. Created interaction (child). See screenshots:
1) Created group
2) Checked VMs are included in the preview:
3) Created a new dashboard with container overview and object list. Checked children mode and object filter for VMs:
4) Now when I select the container it shows VMs:
Most common errors: Child mode is not selected, Filter not properly set, interaction not saved. Hope this is helpful!