In the Visualizer, if the relationship type is 'Connects to', then 'Cause and Effect CIs' filter lists only one CI for all hierarchy levels.
For example. If there are 2 CIs named TestA and TestB with a 'connects to' relationship, it shows only one CI as below:
The 'connects to' relationship is a peer to peer relationship which is why the Cause and Effect AND Root Cause filters do not show all the CIs. The Cause and Effect CIs filter combines impact analysis and root cause in one search. However, the Browse Filter displays an unfiltered view of all CIs. To view all the CIs, you must use the "Browse Filter" filter option as shown below:
This functionality is by design and cannot be altered.